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Equipment Discussions >> Eyepieces

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erik
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List of Paracorr settings for all brands of EP's
      #1744502 - 07/28/07 06:25 PM

Feel free to list the optimum paracorr settings for any brand and f/length eyepiece, based on your firsthand experience. To make this thread most useful to those browsing through it, please limit your posts to something like this:

35mm 2" XYZ brand Oober ultra wide eyepiece- Setting "2"

Thanks!


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP's new [Re: erik]
      #1744814 - 07/28/07 09:49 PM

Though it is admittedly only for TeleVue eyepieces, this TeleVue Paracorr tunable top settings chart should make a good opening addition to this thread:

TeleVue Paracorr tunable top settings chart

The chart is about 3/4 of the way down on the linked page.


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square_peg
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1746443 - 07/29/07 07:15 PM

Meade 5K 34mm SWA - Paracorr setting 2
Siebert 34mm Observatory Series - Paracorr setting 1
Meade 36mm QX - Paracorr setting 1


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ausastronomerModerator
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Re: List of Paracorr settings for all brands of EP new [Re: square_peg]
      #1746462 - 07/29/07 07:29 PM

14mm Pentax XW #1
20mm Pentax XW #1

I don't use the paracorr with the 5mm,7mm and 10mm Pentax XW's

Clear Skies


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: ausastronomer]
      #1746551 - 07/29/07 08:27 PM

Meade Series 4000 UWA:
14mm--5
8.8mm--1
(to be honest, I might have those reversed, but those 2 eyepieces require the extremes when used as 2" eyepieces fully inserted).
Note: The Paracorr has a 43mm lens to shoulder distance at the in-most setting. These two Series 4000 UWAs cannot be used with 1-1/4" filters without hitting the Paracorr's lenses, so the use of these eyepieces in a Paracorr requires the use of 2" filters on the bottom of the Paracorr. If you must use 1-1/4" filters on these eyepieces, use spacers on the 2" barrels to stand the eyepieces out more. This will require different settings on the Paracorr, and the one requiring the most inward position will no longer reach the best position for correction of coma.


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: ausastronomer]
      #1746553 - 07/29/07 08:29 PM

14mm Meade Series 4000 UWA, setting #1 when used in 2" mode.

This is purely from memory, and from my recollection that the 14mm Meade requires a bunch of out-travel of the focuser. Or was it my 8.8mm Meade Series 4000 UWA which required all the out-travel??? Hmmm??? I may also have these reversed.


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asian_hillbilly
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1747079 - 07/30/07 01:26 AM

Quote:

14mm Meade Series 4000 UWA, setting #1 when used in 2" mode.




Yup, that's the setting I always use. When using the 14mm without the Paracorr, I have to pull the 2" skirt out a bit to be able to reach focus.


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walt r
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Re: List of Paracorr settings for all brands of EP new [Re: erik]
      #1748645 - 07/30/07 09:07 PM

I have worked out an equation for the Paracorr setting.

The setting = (0.365 + adp tk - dim f)/0.12


Where:
0.365 = three combined measurments of the Paracorr.
(I'll explain futher if anyone wishes.)

adp tk = flange thickness of the 1.25 to 2 inch adpter used.
0 if using a 2in ep.
0.16 in for the old style paracorr adapter.
I don't have this dimension for the new style. I'll add it if someone will measure it and send it to me.

dim f = the distance of the eyepiece focal plane (field stop) below the top of the ep barrel (surface that sets of the top of the draw tube).
Positive = focal plane inside draw tube,
negative = focal plane above draw tube.
(see TeleVue ep specs for a drawing, bottom of page).

walt

Edited by walt r (07/31/07 09:15 AM)


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: walt r]
      #1757078 - 08/04/07 07:23 AM Attachment (604 downloads)

I woke up early this morning and I've been attempting to make a spreadsheet to calculate the ideal Paracorr tunable top setting based solely upon the field stop location of the eyepiece, and although in its present state it appears to give correct answers for all of the 2" TeleVue eyepieces, it gives incorrect answers for all of the 1.25" TeleVue eyepieces. I've attached it here. It was generated in UNIX, and not using Excel, but I saved it in an excel format, so I hope it looks normal on your computer. If not, please let me know. Feel free to massage or alter it at will, as you may find a better solution than I have found, and you may just solve the 1.25" eyepiece problem as well. So far the only way I have gotten 1.25" eyepieces to read correctly is to multiply the added height from the 1.25" adapter by a factor of 3. This modification however is not present in the spreadsheet as given here, as it seems to have no reason for being so.

The only permitted user input is for:
1) Field Stop location in inches (remember to apply the proper +/- sign for this value)
2) 1.25" eyepiece adapters added height in inches (zero for no adapter, as with 2" eyepieces)

Once you have entered these two parameters, read the spreadsheets calculated value for your eyepiece on the extreme right hand side. Then compare this value with the nominal values provided for the various Paracorr settings, and choose the Paracorr setting for which the provided value most closely matches the value as seen on the extreme right for your eyepiece.


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1757439 - 08/04/07 12:20 PM

My first assumption is that the only function of the tunable top is to maintain a more or less constant distance from the eyepieces field stop location to the Paracorr's lens group, with deviation from this optimal distance leading to somewhat less than optimal Paracorr performance. Part of my difficulty in making my spreadsheet (see above post) is that I have sold my Paracorr, and I can not measure this distance, and therefore must guess. I must also guess at the height range provided by the tunable top, and my guess here was 1/2 inch.

TeleVue gives us a chart (reference my first post in this thread for the link) of optimal Paracorr settings, but for 1.25" eyepieces this chart is seriously flawed by the fact that apparently 2 quite differing heights of TeleVue 1.25" to 2" adapter are (or at least were) available for the Paracorr, and the TeleVue table does not specify which adapter they used for the chart. Whichever adapter they used, if you have the other one, then the TeleVue chart is pretty much useless in providing you with the best setting for your 1.25" eyepieces.

One of the adapters has a set-screw which fits into a recessed slot, and is thus of a low profile, and the other adapter does not, and is therefore high profile. Both are pictured along with the Paracorr's as seen above the TeleVue website Paracorr tunable top chart.

Most budget after market 1.25" to 2" adapters are of the high profile variety.


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1757457 - 08/04/07 12:34 PM

If my assumption is correct (and it does work to give correct tunable top settings for all TeleVue 2" eyepieces when used in 2" only mode), then I will perhaps never understand why TeleVue chose to place their 1.25" eyepieces where they did upon their tunable top chart.

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walt r
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1757514 - 08/04/07 01:16 PM

Ok, I think I know where the problem is. Look at the pictures of the ParaCorr parts on TeleVue's web site. They have two different tunable tops with different height 1.25 to 2" adpaters. The old style is 0.16 in thick. The new style is much thicker (I don't have one to measure but it looks to be about 3X the old adapter). In the equation in my post above, the TeleVue ParaCorr setting do work out for all of the 1.24" eyepieces if the adpter thickness is set to 0.37 inch. I did check the above posted equation in a spreadsheet for all of the eyepieces in the ParaCorr Setting Chart (the chart is not correct for 1.25 eps using the old adpter thickness, decrease the setting by 2 is close to correct). Also note that TeleVue states that "set path length from Paracorr flange surface to CCD surface to 55mm 4mm for best results". 4mm = 0.157in, whereas a chenge from one setting to the next = 0.12in. This 1.3 settings, so there appears to be a fairly wide tolerance to get the correct setting.
Would you like a copy of my speadsheet?
walt


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: walt r]
      #1757641 - 08/04/07 02:22 PM

Yes, please either attach it here, or PM me. An attachment would let others assist here as well.

I see now that if the 1.25" to 2" adapter which TeleVue actually used to generate their chart is in fact 3 times thicker (higher in profile) than the one I assumed they used (using your provided 0.16" figure, I had assumed the low profile model), then my spreadsheets results are highly accurate just as it is written and attached above for all TeleVue eyepices, and the fudge factor of 3 times the height for the adapter (which I refused on logical grounds to include in my spreadsheet) is in fact unnecessary. The pictured high profile adapter on the TeleVue Paracorr website does indeed look visually to be every bit of a full 3 times thicker than the low profile adapter sitting beside it.

By inference, my initial fundamental assumption is correct, and by further inference, any non TeleVue eyepiece which comes to focus in close proximity to an existing TeleVue eyepiece will thereby share that TeleVue eyepieces recommended (or spreadsheet derived) Paracorr tunable top setting.

Also, since most after market 1.25" to 2" adapters are of the high profile variety, the TeleVue chart is useful for them as well. My spreadsheet will work for all adapter heights, so those with unique adapters need not worry.


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walt r
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1758433 - 08/04/07 10:37 PM Attachment (898 downloads)

See attached Excel Spreadsheet.
Have fun.

walt


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: walt r]
      #1758657 - 08/05/07 01:38 AM

Just measured adapter on current Paracorr: 0.379" or 9.69mm.
Hope that helps.


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1758682 - 08/05/07 02:20 AM

Excellent, thanks a bunch Don!

To all:
I would like to know a few more measurements for specifically the Visual Paracorr model which comes with the taller 0.379" high 1.25" to 2" eyepiece adapter:

CAUTION / WARNING: Whatever anyone willing to undertake these measurements may do to achieve them, please do not scratch your Paracorr in the process.

1) With the Paracorr at setting #1, what is the distance from the top (eyepiece shoulder) to the first (eye) lens element (on axis if possible).

2) Ditto for setting #3

3) Ditto for setting #5

(and ditto with bonus points for settings #2 and #4 if you are brave)

For those less brave (or should I say foolhardy), simply providing the total tunable top span distance from setting #1 to setting #5 would be a great help (I.E. the total travel distance of the tunable top itself, which is the measure of the gain in overall length of the Paracorr). Another great help would be answering if the individual settings gain distance linearly, or non linearly (in which latter case knowing the actual gain in height (length) for each setting would be great).


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1764062 - 08/07/07 04:20 PM

Second plea: I'm now willing to accept much less than before. Will anyone simply measure the total travel span distance (overall height increase from lowest to highest setting) for their modern style (high profile adapter model, the one with no recess slot for the adapters set-screw) Visual Paracorrs tunable top? This is a non-destructive measurement.

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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1764186 - 08/07/07 05:24 PM

Quote:

Second plea: I'm now willing to accept much less than before. Will anyone simply measure the total travel span distance (overall height increase from lowest to highest setting) for their modern style (high profile adapter model, the one with no recess slot for the adapters set-screw) Visual Paracorrs tunable top? This is a non-destructive measurement.



Lawrence:
Height of top of Paracorr w/o adapter, setting 5(low): 1.545"
Height of top of Paracorr w/adapter, setting 5: 1.920"
Length of insertion tube part of Paracorr: 2.39"
Height added to top when adjustable top is in highest position: 0.5" (Setting 5=0", setting 1 =0.5" up), each setting increases by 1/8" on smooth, even ramp. Setting 4=+1/8", Setting 3=+1/4", Setting 2=+3/8", Setting 1=+1/2".
I vaguely recall, when I was using Meade Series 4000 UWA eyepieces in the Paracorr, that the maximum depth of an eyepiece that wouldn't hit the lens in position 5 (the lowest setting) was 43mm (1.7"). I don't recall if that was being conservative so as not to risk the lens or whether or not that was actually the distance from lens center to 2" shoulder in setting 5. I do know that I could not use 1-1/4" filters on the Meade 14 or 8.8 (which had the same height of barrel, though it was the 8.8, I guess, that used position 5) without hitting the lens. So if you have one of those to measure, the distance to lens is definitely larger than that length.
I don't have any way to measure that distance without risking a scratch on the lens. Sorry.


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1764262 - 08/07/07 06:05 PM

Don, Thank you again!

Just to clarify. Are you saying that both the 14mm UWA and 8.8mm UWA when used in 2" mode would safely fit into the Paracorr while at its lowest tunable top setting and without a filter screwed on, but at least one of them (if not both) would most certainly hit the lens of the Paracorr with a filter screwed on?

If this is correct, then can someone who has these eyepieces tell me what their length is from the focuser shoulder to the end of the 1.25" barrel section? Perhaps just standing them up on a table top and carefully measuring from the table top to the focuser shoulder would be the easiest means to accomplish this.


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1764287 - 08/07/07 06:24 PM

One "relatively" safe means to measure the insertion depth of a late model Visual Paracorr while at its lowest height setting on the tunable top would be to simply place a cotton 'Q'-tip down the side until it rests by gravity on the lens element, and then mark it at the shoulder junction. Then remove it, and stand it up (without any downward force applied), and measure from the table top to the mark on the 'Q'-tip.

CAUTION / WARNING: Again, I warn that I would not wish or intend that anyone scratch a Paracorr in attempting to measure it.


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1764592 - 08/07/07 08:40 PM

Quote:

Don, Thank you again!

Just to clarify. Are you saying that both the 14mm UWA and 8.8mm UWA when used in 2" mode would safely fit into the Paracorr while at its lowest tunable top setting and without a filter screwed on, but at least one of them (if not both) would most certainly hit the lens of the Paracorr with a filter screwed on?

If this is correct, then can someone who has these eyepieces tell me what their length is from the focuser shoulder to the end of the 1.25" barrel section? Perhaps just standing them up on a table top and carefully measuring from the table top to the focuser shoulder would be the easiest means to accomplish this.



Exactly. The addition of a typical filter (Meade, Orion, etc.) would hit the lens--in the lowest setting of the Paracorr.


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1764599 - 08/07/07 08:47 PM

Quote:

One "relatively" safe means to measure the insertion depth of a late model Visual Paracorr while at its lowest height setting on the tunable top would be to simply place a cotton 'Q'-tip down the side until it rests by gravity on the lens element, and then mark it at the shoulder junction. Then remove it, and stand it up (without any downward force applied), and measure from the table top to the mark on the 'Q'-tip.

CAUTION / WARNING: Again, I warn that I would not wish or intend that anyone scratch a Paracorr in attempting to measure it.



Depth is 49mm or 1.93"(about as accurate as I can be) between center of lens and shoulder of 2" insertion barrel, tunable top in place at its lowest setting.
Thanks for the Q-Tip idea--I went ahead and cleaned the lens at the same time. It had a lot of dust on it.


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1766582 - 08/08/07 07:08 PM Attachment (486 downloads)

Here (attached) is my final spreadsheet. It assumes that with the Paracorr at a midrange setting of 3 the distance from the eyepiece shoulder flange of the Paracorr to the focal plane of the Paracorr is the ideal 55mm as specified by TeleVue. This plus a bunch of help from Don has taken my spreadsheet out of the realm of empirical, and into the range of being precise in its attempt to choose the optimal tunable top setting which achieves the closest to the ideal of 55mm spacing between the focal plane (FP) of the Paracorr and the focal plane (FP) of the eyepiece. Oddly, though it is in quite high agreement with the TeleVue eyepiece chart for the Paracorr setting of choice (even for the use of the 1.25" adapter), it is not 100% exact. Being quite biased, I'm personally inclined to believe my own spreadsheet in the few areas where it differs from TeleVue's suggestion for the ideal tunable top setting. If you had previously downloaded my earlier attempt at this spreadsheet, please delete it and replace it with this one. The moderators have my permission to eliminate my earlier spreadsheet attachment (post and all if necessary).

As always, please let me know if my UNIX based "OpenOffice" spreadsheet software translates this properly to the Microsoft Excel format. Despite my best efforts to save things in the proper Excel format, sometimes the translation gets a bit jumbled in its formatting, formulas, etc... Excel is not available in UNIX......

As always, kick the tires, and feel free to fix any mistakes I may have made, or improve upon my ideas as you see fit.

Edited by Lawrence Sayre (08/08/07 08:39 PM)


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1766628 - 08/08/07 07:36 PM

Lawrence,
Worked fine. Excel converted the spreadsheet into the latest version of Excel.
I utilized the empirical method to decide the optimum Paracorr setting for each of my TeleVue eyepieces rather than trust TeleVue's spreadsheet that showed the proper setting.
I started at the outmost (1) setting and focused, examined the edge, moved in one setting (2), focused and examined the edge, repeating the process through all 5 settings if necessary.
If two settings seemed to have equal edge correction, I tried the in between setting (e.g.2.5) to see if the correction was better.
All my eyepieces are Naglers now, but I had a Panoptic at the time, and some series 4000 Meade UWAs. My empirical results pretty much agreed with TeleVue's. A couple of the eyepieces' best settings were in between settings, I thought, but the TeleVue recommendations would be fine for their eyepieces in my f/5 scope. At shorter f/ratios, coma correction becomes more critical and residual coma is visible even in a Paracorred eyepiece. In such cases, an in-between setting might become more important.
I put a small marker label on each eyepiece with the proper Paracorr setting, and marked the 1-5 settings of the Paracorr with numbers as well. Now, when I take an eyepiece out of the case, I merely match number with setting--no memory involved.
In the cases where settings 1 or 5 were chosen as the best candidates, I've often wondered if having the tunable top move a little farther in each direction would result in improved coma correction. In other words, I'd have been happier with 7 settings where all my eyepieces' best corrections were settings 2-6. Your spreadsheet could have answered the question if you allowed it to calculate the optimum position rather than the optimum setting.

Edited by Starman1 (08/08/07 07:38 PM)


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astrodon
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1766645 - 08/08/07 07:43 PM

Thanks for the work guys!

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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: astrodon]
      #1766771 - 08/08/07 08:50 PM

OK guys, I really hate to do this to you, but I just changed my spreadsheet once again to fix a glitch, so if you downloaded a copy of my "final" version prior to my 8:39 PM today revision time as listed in my above post with the attached spreadsheet, please go to that same post above and download it from there once again.

One interesting thing I discovered is that in its final (I hope) form, I can now definitively conclude that the spreadsheet/chart output which TeleVue has posted on its website is in fact for the much older version of the Visual Paracorr which came with the much lower profile 1.25" to 2" adapter (which is 0.16" high). Therefore in its current form, the TeleVue chart on their website is not usable for 1.25" eyepieces in conjunction with the higher profile adapter models (which I believe may have came about when the compression ring was added to the adapter). This makes sense, as the chart has been around for a good while, and the compression ring adapter is the new kid on the block so to speak.


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walt r
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1767558 - 08/09/07 10:10 AM

Don,
The Spreadsheet I posted does show the optimum setting even if its negative or larger than 5.
walt


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1767803 - 08/09/07 12:08 PM

Lawrence,
I have a question about your spreadsheet:
On the TeleVue site, TeleVue shows the setting for the 1-1/4" Type 6 Naglers as setting 4. It also shows that the field stop for each of these eyepieces is 0.25" below (toward the field lens end) the eyepiece "shoulder" (where the inserted eyepiece sits).
Do I enter this as a positve (as TV shows on their site) in your calculator, or as a negative?


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: walt r]
      #1767817 - 08/09/07 12:16 PM

Quote:

Don,
The Spreadsheet I posted does show the optimum setting even if its negative or larger than 5.
walt




Walt,
Your calculator showed the proper setting for the Type 6 Naglers as 4.11 with the new adapter. My empirical test done with the 13 showed setting 4 as the best setting.
So there's a general agreement between your formula and what I see at the eyepiece for these 1-1/4" Naglers.

Lawrence's calculator showed setting 2 or 1 (depending on how the field stop distance from the shoulder is input), which didn't match with what I see.

Your formula is easy to use for an eyepiece whose field stop position can be determined. But many new eyepieces don't have such information available. The old empirical method would seem to be the only choice in those cases.

However, on the 2" Naglers, the results from your calculator are diffierent than TeleVue's claims, but I understand why. For example, I get a setting of greater than 6 for my 31 Nagler, which makes sense, I guess. The field stop of that eyepiece is 0.38" ABOVE the shoulder, which means the field stop-to-lens distance is 58.65mm in setting 5. Since the optimum is 55mm, the 31 Nagler should go 3.65mm further into the barrel to achieve the optimum setting (i.e.an imaginary setting 6). Setting 5 is just the best the Paracorr can do for that eyepiece.

I like the calculator. It works.

Edited by Starman1 (08/09/07 12:26 PM)


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1767860 - 08/09/07 12:37 PM

One more point about Walt's calculator:
The divisor should be 0.125 instead of 0.12
It defines the difference between each setting in inches, and I measured 0.125" between settings, not 0.12".
The results are the same, so I'm being persnickety.


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1768077 - 08/09/07 02:19 PM

Don,
I forgot that you got the 0.125 measurement for the new style ParaCorr. I have the old style and measured a difference of 0.48 inch from setting 1 to 5. That's 0.12 inch per setting.

My best guess is that there are some dimensional differences between the old and new style ParaCorrs beside the diffence in the 1.25 to 2" ep adapter.

walt


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1768155 - 08/09/07 03:12 PM

Quote:

Lawrence,
I have a question about your spreadsheet:
On the TeleVue site, TeleVue shows the setting for the 1-1/4" Type 6 Naglers as setting 4. It also shows that the field stop for each of these eyepieces is 0.25" below (toward the field lens end) the eyepiece "shoulder" (where the inserted eyepiece sits).
Do I enter this as a positve (as TV shows on their site) in your calculator, or as a negative?




Don,

Below is positive, and above is negative. This is the same as TeleVue's convention.


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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1768193 - 08/09/07 03:31 PM

Lawrence,
Then something isn't working in your calculator.
Example:
55mm (2.165") is the optimum field stop-to-lens distance on the Paracorr.

The depth of the Paracorr is 49mm (1.929") and the height of the 1-1/4" adapter is .379". That would be 2.308" at setting 5 (all the way in). A setting of 4 (+0.125") would yield 2.433".

The Type 6 Naglers have a field stop 0.25" into the 1-1/4" lower tube, so I subtract that from 2.433" to yield 2.183", only 0.018" from the perfect location.

TeleVue's website says position 4 is optimum for the Type 6 Naglers.

Your calculator derives a setting of 2 for those eyepieces. Walt's derives a setting of 4, like TeleVue's recommendation.


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1768271 - 08/09/07 04:28 PM

Starman,

The distances are what they are, and all of this is really quite simple (being nothing but straightforward distance addition and subtraction). I've already explained that the chart on the TeleVue website dates to the older pre-compression ring Paracorr with the low profile adapter. For this adapter it gives the proper setting of position 4 for all of the 1.25" eyepieces with the field stop 0.25" below the focuser shoulder. This is a natural outcome of my finally having done it right.

The conclusion which I have reached is that for the newer model Paracorr and adapter the optimal 1.25" TeleVue eyepiece setting is in fact setting 2 (for all of their 0.25" below the shoulder FP position 1.25" eyepieces). The reason for this is straight forward. Add 1/4" to the height of the adapter, and the FP of the 1.25" eyepiece is thereby moved 1/4" farther away from the 55mm optimal. To counter this, the Paracorr must be screwed in 2 full notches to make it 1/4" shorter. Of course none of the 2" eyepieces are affected by any of this.


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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1768310 - 08/09/07 04:49 PM

Lawrence,
If you read my post, you will see I used the dimension from the newest adapter, with the .379" thickness to show that the Type 6 eyepieces optimally use setting 4 of the Paracorr, which is what TeleVue suggests. My Paracorr's instructions even have a cross-section of the Paracorr pictured, showing the new adapter.
Simple arithmetic shows setting 4 is correct for these eyepieces with the new adapter.
My empirical test also showed setting 4 produced the best correction.
Hence, there is an error somewhere in the calculator if it suggests setting 2 is optimum.

By the way, if the newer adapter is thicker than the older adapter, that would raise the eyepiece away from the lens, necessitating a closer setting of the Paracorr with the thicker adapter. If the thinner adapter used setting 4, the new adapter would require a setting 6 in order to get close enough to the lens. So your contention that the older, thinner adapter used setting 4 and the newer thicker one setting 2 is illogical.
Remember, setting 1 is the farthest from the lens.

Rereading your post, I see we are talking about the same direction, and that you have merely reversed the order of the settings. 5 is closest, and 1 is farthest, not the other way around.

Edited by Starman1 (08/09/07 04:53 PM)


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1768329 - 08/09/07 05:06 PM

Starman, is not 5 the highest (longest) setting, and 1 the lowest (shortest) setting, or am I looking at the Paracorr completely backwards? If the eyepiece is lifted 1/4" "more" away from the Paracorr by the new adapter, then to erase this 1/4" increase in the distance between their respective focal planes the Paracorr itself must contract in length by 1/4".

Obviously the TeleVue website chart of Paracorr settings can only be correct for one of the two possible adapters. Does anyone recall this chart suddenly changing at some point?


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1768394 - 08/09/07 05:43 PM

I sold mine awhile back. Will anyone who currently owns a Paracorr with a tunable top tell me which numeral (setting) corresponds to the shortest overall length of the Paracorr, and which corresponds to the greatest overall length?

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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1768484 - 08/09/07 06:49 PM

Lawrence,
5 is the lowest setting, with the tunable top screwed in to make the Paracorr shortest.
1 is the highest setting, with the tunable top screwed out to make the Paracorr longest.
Since the screw doesn't move, the leftmost slot position is 1 and the righthand slot position is 5. The slot tilts uphill toward the right, allowing the tunable top to come in (down) as a higher number is dialed.
Don


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1768486 - 08/09/07 06:51 PM

Or, another way:
5-- 0"
4-- +1/8"
3-- +1/4"
2-- +3/8"
1-- +1/2"


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1768497 - 08/09/07 06:56 PM

Don, somehow I don't intuitively get that from looking at this photo:

Paracorr with tunable top

And how can anyone explain that the spreadsheet gives correct output for 2" eyepieces, while not working for 1.25" eyepieces? The laws of optics are the same for both, so the math which works for one must work for the other, no?


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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1768673 - 08/09/07 08:42 PM

Lawrence-
In the photo of the Paracorr with the tunable top you can see that setting 5 is the lowest, for in order to reach that setting the tunable top with the slot in it must descend in order for the set screw to reach that level.
Hope I helped to clear this up, I know it is hard to get just by looking at the image,
~Don


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: astrodon]
      #1768777 - 08/09/07 09:31 PM Attachment (429 downloads)

OK, I finally realize that my intuitive view of the 5 being higher in the picture than the 1 was all wet, and I now trust that 5 is the lowest and 1 is the highest setting. Obviously the slide lever has to go up for the tunable top to go down, and visa versa. Thank you Don and Don!!! With that to go on, I've re-worked my spreadsheet once again, and I'm attaching it right here. I'm also now willing to believe that the TeleVue website chart is using the taller adapter for its 1.25" eyepieces. Please kick the tires with this spreadsheet, and let me know if it gives correct tunable top settings across the board.

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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1768841 - 08/09/07 09:57 PM

Lawrence,
It worked for my 31 Nagler and my Type 6 Naglers.
It didn't work for the 17 Nagler, with a field stop to shoulder dimension of -0.03"
The spreadsheet erroneously gives a setting of 5 instead of 3.


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1768866 - 08/09/07 10:07 PM

Lawrence,
I accidentally included the adapter height for a 2" eyepiece.
Doh!
Your calculator works fine.
Don


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Lawrence Sayre
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1768948 - 08/09/07 10:55 PM

Thanks!!!

Whew, you had me worried there for a bit. I was beginning to wonder if I would ever get it right. A sanity tester for sure.


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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1786829 - 08/19/07 02:17 PM

for the 30mm 1rpd, setting 3, works suprisingly well. When I later aquired the real deal 30mm widescan III, suprisingly, it wasnt as well correctable with the paracorr, possibly because it has a wider field stop. I kept both eyepieces. Since I also aquired a nice f10 OTA, I use the WSIII with it, and my most recently aquired 31mm nagler with the dob, with or without the paracorr. I have the older photo/visual model, and the vignetting bothers me, so I will likely add the visual model in the future, and keep the other for my 8"f4 for imaging.

my 2c in the 8.8 UWA discussion, I used it in the lowest setting (5) with the included 1.25 adapter in 1.25 mode, like suggested for the 9mm nagler and it worked very well. I dont think I tried it with the 14mm yet, which I aquired more recently.


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Re: List of Paracorr settings for all brands of EP new [Re: Keith]
      #1787397 - 08/19/07 07:10 PM

I went back and looked for my records:
14mm UWA (used as 2")--setting 1
8.8mm UWA (used as 2")--setting 5

The 31 Nagler would be better corrected at setting 6. The fact there is no setting 6 shows the Paracorr was designed long before the 31 Nagler. I find it "tolerable" with setting 5, however.


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1799454 - 08/25/07 11:49 AM

Thanks Don,

You just saved me a lot of work. I have both of those EPs and a brand new Paracorr PCV-2000 still snug in the box waiting for dark skies.


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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1805439 - 08/28/07 11:54 AM

Quote:

I woke up early this morning and I've been attempting to make a spreadsheet to calculate the ideal Paracorr tunable top setting based solely upon the field stop location of the eyepiece, and although in its present state it appears to give correct answers for all of the 2" TeleVue eyepieces, it gives incorrect answers for all of the 1.25" TeleVue eyepieces.




Probably means you haven't accounted for the extra 9.6mm caused by the Paracorr 2"-1.25" adapter.

Edit: never mind - late to the party...


Edited by sixela (08/28/07 11:56 AM)


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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #1885054 - 10/04/07 08:36 AM

What about Ethos?

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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: bkushner]
      #1885980 - 10/04/07 02:49 PM

The position of the Ethos' focal plane is only 0.02" different than the Type 6 Naglers. That means setting 4 would be correct--the Nagler Type 6s WITH the adapter, and the Ethos WITHOUT an adapter.
I don't believe you could get the Ethos close enough to the Paracorr lens if used with a 1-1/4" adapter.


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sixela
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1886417 - 10/04/07 05:55 PM

Can't. In 1.25" mode in a 2"-1.25" adapter, it doesn't insert with the 1.25" barrel completely seated in the adapter, because the 2" barrel contacts the adapter.

When used this way, the focal plane is much too far from a Paracorr lens, even with a zero-length adapter.

Ethos: 2" mode, top fully pulled out.


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Re: List of Paracorr settings for all brands of EP new [Re: sixela]
      #1887162 - 10/04/07 11:30 PM

It works fine in a TeleVue "High-Hat" 1-1/4" adapter, but, in general, the Ethos should be used as a 2" eyepiece in 2" focusers. And in the Paracorr too.

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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1887870 - 10/05/07 11:08 AM

Anybody know offhand what the settings for the 14, 10.5 and 7 mm Pentax XLs is?

I say "is" because they are all parfocal.



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sixela
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1888469 - 10/05/07 03:10 PM

Quote:

It works fine in a TeleVue "High-Hat" 1-1/4" adapter,




That doesn't fix the issue either, because the reason it works is because the high-hat adds extra length.


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1888566 - 10/05/07 03:46 PM

Quote:

It works fine in a TeleVue "High-Hat" 1-1/4" adapter, but, in general, the Ethos should be used as a 2" eyepiece in 2" focusers. And in the Paracorr too.




That's what TV's Ethos instruction sheet plainly says....


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Re: List of Paracorr settings for all brands of EP new [Re: Mr. Bill]
      #1990375 - 11/16/07 09:02 PM

Quote:

Anybody know offhand what the settings for the 14, 10.5 and 7 mm Pentax XLs is?

I say "is" because they are all parfocal.






The Pentaxs appear to perform best with the tunable top set to the highest setting (which requires the max amount of focuser in-travel). I had to cut 15mm from my truss poles to accommodate but its worth it

I find the paracorr works wonderfully as a field flattener, nicely mitigating the often criticised field curvature in the 14 and 21mm pentaxs

A note of caution! A friend handed me an OIII filter to try on my 31nagler. Dont try it as it hits the paracorr lens



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Re: List of Paracorr settings for all brands of EP new [Re: Starkler]
      #1990803 - 11/17/07 01:31 AM

Quote:


A note of caution! A friend handed me an OIII filter to try on my 31nagler. Dont try it as it hits the paracorr lens





Ouch.
Note: 2" filters should be threaded on the bottom of the Paracorr for safety's (and convenience's) sake.
And don't use 1-1/4" filters on the bottom of the dual 1-1/4"/2" eyepieces when used as 2" eyepieces either. The filter will hit the lens if a lower setting is used.
If you use a Paracorr, it is safer to use all 2" filters and thread them on the bottom of the Paracorr.


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #1993128 - 11/18/07 09:24 AM

For that reason I'm designing a 2" filter wheel that goes right below the ParaCorr.

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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #2054266 - 12/16/07 07:50 AM

Lumicon sells thier coma correcter for about 100 euros less than TV's paracorr in France, I'd love to hear if anyone has done a side by side comparison!

Shawn Haggerty Avignon, France


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Re: List of Paracorr settings for all brands of EP new [Re: Shawn H]
      #2054585 - 12/16/07 11:22 AM

The Lumicon has a full-aperture lens, so it won't vignette, but adjusting the eyepiece focal plane to lens distance will require the use of spacers, because there is no adjustment there. The Lumicon was designed as a photographic accessory where the distance from the camera's focal plane to the lens is set once and forgotten. Unfortunately, different eyepieces have their focal planes in different spots and some method of adjusting the lens to focal plane distance is needed.
Because of the lens design (it's a Ross), there will be more spherical aberration on axis, though somewhat better coma correction at the edge of the field.
But note: even if not perfect, applying coma correction, whether dialed in or not, to the image in a short focal ratio newtonian will result in better images than without it.
For visual use, nothing beats the Paracorr. But if you're correcting the image for imaging, the Lumicon, Baader, and TeleVue will all work wonders. And all are better than nothing.


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #2136375 - 01/21/08 05:31 PM

what image degradation will happen if the 55mm distance between the paracorr lens and the eyepiece field stop is not maintained?, if there are eyepieces with focal planes that will increase or decrease the 55mm distance beyond the 55 +\- 4mm tolerance coma correction won't be optimal, but what about other abberiations, such as spherical abberiation?

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Re: List of Paracorr settings for all brands of EP new [Re: V.A.]
      #2137866 - 01/22/08 11:49 AM

Coma correction will be less, and spherical aberration will be added. However, a less-than-optimum setting still works OK. Nagler's own 31mm Type 5 requires a setting 1/8" farther in than the Paracorr can be set, yet the correction is still superior to the eyepiece by itself. What small amount of spherical aberration that is added is a small price to pay for such a significant amount of coma reduction and some field flattening.

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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #2143170 - 01/24/08 06:46 PM

I recently purchased a Paracorr for my f4.8 dob, and really appreciate this thread. I'm working to find the best settings with various EPs, with no problem for most of them. But I am having a hard time finding field stop data for some, and thus, can't run the calculations -- although I will likely discover the best Paracorr settings by trial-and-error.

Anyone have personal knowledge of Paracorr settings for Vixen LVW 17mm and Pentax XF 12 and 8.5mm?

Thanks in advance,


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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #2148029 - 01/26/08 09:11 PM

Thank you Lawrance.

With your spreadsheet, I could calculate the tunable top positions for my eyepieces.

Pentax XW 7: setting 1
Pentax XW 20: setting 1
Speers-Waler 5-8 variable: setting 1
Pentax XL 40: setting 3.


Edited by Denimsky (01/27/08 12:06 PM)


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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #2202492 - 02/19/08 10:44 AM

Looking for a sanity check...

I worked through the spreadsheet but want to check out the results (might be locked up). I get setting 5 for a TV new model paracorr with the stock 1.25" adaptor and my 14mm Meade 5k UWA?

Took the advice on filters, ended up using my O-III filter laid over the top of the eyepiece...need to acquire some 2" filters...

Thanks in advance...


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #2227947 - 02/29/08 07:27 PM

i was looking at the parrcorr about that issue your having with the 31mmt5 not reaching it's optimal position. there's a ridge on top of the tunable top that the eyepiece rests on, it's about .2" tall, right above the brass ring. it could be machined down by .125" to bring the 31t5 to it's optimal position. this would make the #5 setting to #6 and you would loose the #1 position (or do i have the numbers backwards?) , but it seems like it will work fine and it's a very simple modification.

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Re: List of Paracorr settings for all brands of EP new [Re: V.A.]
      #2228539 - 03/01/08 01:08 AM

Yes, the lip of the tunable top could be machined down.
I have eyepieces that use 1-5 now. I'd have to extend the tunable top's slot to allow more movement up to make that modification, though.
The correction may not be perfect, but it is fine for the low power use in my f/5 scope. Were my dob larger and faster (generating more magnification for the 31 and more coma to correct), position 5 might not be adequate. But, though it is 1/8" away from the perfect position, it certainly works OK for that eyepiece.
I have a machinist friend who might be able to make a tunable top for me with the necessary travel and shape, and I'd love to get rid of the compression ring and have a nice snug fit instead with a 1/4" nylon screw eyepiece tightener.


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #2229399 - 03/01/08 02:22 PM

i think i may have overlooked the antireflection threads inside the parrcarr, it seems like the eyepiece barrel might hit the threads before it will go down any further, so the modifications are a little more extensive than i first thought, the antireflection threads would need to be machined down a little as well.
on a diffrient note, i noticed when holding the parrcorr in front of my eyes and looking through it ,the parrcorr seems to have a positive focal lenght, i can actually place an eyepiece in front and it will form an image. how does it extend the focal lenght by 1.15x when it appears like it would act as a focal reducer? there must be some optical principals i'm unware of.


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: V.A.]
      #2229530 - 03/01/08 03:49 PM

Well, in the aggregate, it has to perform like a slightly negative lens in order to have a positive magnification effect.

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Mike Foreman
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Re: List of Paracorr settings for all brands of EP new [Re: Shawn H]
      #2457110 - 06/12/08 11:42 PM

Does anyone know the in focus of a Paracorr?
With the 26nT5 I can focus without it but can't focus with it.
I am trying to calculate how much to trim off my truss tubes.

BTW I am using an 18" f:5.


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walt r
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Re: List of Paracorr settings for all brands of EP new [Re: Mike Foreman]
      #2457710 - 06/13/08 11:00 AM

An update on using a N12T4 with the barrel extension.

Note: I have an older Paracorr with the tunable top.
Check this procedure using the technique of starting with an EP that has a known setting. Then without moving the focuser, change to the N12T4 and adjust the Paracorr until focused.


When the barrel extension is installed on a N12T4 the extension will bottom out inside the Paracorr and not on the tunable top. This means that the tunable top's setting is meaningless if one just inserts the N12T4 into the Paracorr.

Through experimentation I discovered how to get the proper Paracorr setting on the N12T4 with the barrel extension.

1) The starting setting of the Paracorr is really unimportant but I usually have it at setting three, the mid-setting.
2) Insert the N12T4 into the Paracorr until the barrel extension bottoms in the Paracorr.
3) Tighten the thumb screw to lock the N12T4 to the tunable top.
4) Loosen the Paracorr tunable top lock.
5) Rotate the tunable top to the right (extending the top outward) one setting (or move to the next setting on the left). From setting 3 to setting 2 for example.
6) Lock the tunable top.
The Pararcorr is now set for the N12T4.

Edited by walt r (06/13/08 02:45 PM)


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Mike Foreman
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Re: List of Paracorr settings for all brands of EP new [Re: walt r]
      #2457764 - 06/13/08 11:24 AM

Thanks Walt.
So if I am understanding correctly once the Paracorr is set relative to the telescope then it is a matter of getting the eyepiece set to the Paracorr?


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walt r
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Re: List of Paracorr settings for all brands of EP new [Re: Mike Foreman]
      #2458154 - 06/13/08 02:46 PM

Thats correct Mike. The Paracorr specs are a set distance from the Paracorr lens to the focal plane in the EP. It is the EP's focal plane to external dimensions that differ from EP to EP.
Translated, the Paracorr lens is to be at a fixed distance inside the original focal plane of the primary mirror.


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Starkler
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Re: List of Paracorr settings for all brands of EP new [Re: Mike Foreman]
      #2459114 - 06/13/08 11:49 PM

Quote:

Thanks Walt.
So if I am understanding correctly once the Paracorr is set relative to the telescope then it is a matter of getting the eyepiece set to the Paracorr?




Once you have the correct position for one eyepiece sorted and focused, you can lock your focuser and focus other eyepieces with the tunable top and it will be correct


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Astrolabe
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Re: List of Paracorr settings for all brands of EP new [Re: Starkler]
      #2487391 - 06/28/08 01:13 AM

Thanks to everyone for the work done in the relation to the Paracorr settings. I recently bought a paracorr but I have no problems with the settings as all my eyepieces are made by Televue.
An observing mate wants to try the Paracorr with his Meade 5000 32mm - 2" Plossl and his 21mm Orion Stratus. I haven't any more information on these eyepieces so I cannot use the spreadsheet. I will be gratefull if someone could tell me the paracorr settings for these two eyepieces.

Thanks in advance and regards

George (astrolabe)
Sydney Australia


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: Astrolabe]
      #2487408 - 06/28/08 01:38 AM

Quote:

Thanks to everyone for the work done in the relation to the Paracorr settings. I recently bought a paracorr but I have no problems with the settings as all my eyepieces are made by Televue.
An observing mate wants to try the Paracorr with his Meade 5000 32mm - 2" Plossl and his 21mm Orion Stratus. I haven't any more information on these eyepieces so I cannot use the spreadsheet. I will be grateful if someone could tell me the paracorr settings for these two eyepieces.

Thanks in advance and regards

George (astrolabe)
Sydney Australia



It's easy, mate.
Set the Paracorr for one of your TeleVue eyepieces and focus.
Remove your eyepiece and install his. Refocus using the tunable top and look at the setting. That's the setting for that eyepiece. Write it down. REmove the eyepiece and install the other one. Focus using the tunable top. Note the setting. You can do this for a whole box of unknowns.


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Astrolabe
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #2487817 - 06/28/08 11:19 AM

Don

Your opinion and advice is always valued and appreciated, thank you for the prompt reply.

Best regards

George (astrolabe)


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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #2562583 - 08/05/08 07:47 PM

since we have a bunch of paracorr users here, it seems rather fitting to ask, even if only an opinion, I'm getting a 12" dob f/4.9 and was wondering how necessary paracorr was. i do plan to get an antares 1.6 barlow and some hyperions EPs with it and plan to save up for a 2x powermate and an ethos.

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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: cyberhedz]
      #2562977 - 08/05/08 10:54 PM

Varies. I found coma severe enough at f/5 to require a Paracorr. Other observers don't use one at f/4.5.
Here's a question: Do you want the stars at the edge to be as tight as the center? You'll need a Paracorr.
Don't care about the edge? Probably won't need one.
Don't know the answer?
Look first, buy later. There's no shortage of Paracorrs.


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #2564404 - 08/06/08 04:45 PM

See the following posts for why this post has a mistake in logic...Don

Ethos Paracorr Settings:
TeleVue's recommended settings are incorrect, according to both my eye and the two excellent calculators on this thread.
Here's what I found:

Used as 2" eyepieces in the Paracorr:
13mm Ethos--Setting 1, with the eyepiece pulled out of the Paracorr 1.5mm
8mm Ethos--Setting 1, with the eyepiece pulled out of the Paracorr 12.5mm (not practical unless a 2" skirt is added to the eyepiece)

Used as 1.25" eyepieces in the Paracorr:
13mm Ethos--Setting 4
8mm Ethos--Setting 1 with the eyepiece pulled 2.5mm further out.

It seems TeleVue's recommended settings may have been calculated using pre-production design specs. TeleVue says that the 1.25" settings for the Ethos are 5(13) and 4(8) respectively, and that isn't even close on the 8mm.
I used the empirical method of actually looking at the edge-of-field star images, and the settings I derived agreed with the 2 calculators on this thread.

The focal plane of the 8mm is 0.7" (17.78mm) below the 2" shoulder, or 0.43" (10.9mm) lower in the barrel than the 13.
If the 13 uses setting 1 in the Paracorr in 2" mode, the 8mm is going to need to be at least 10.9mm farther out than setting 1. If used with a Paracorr, there's no way around a lot of infocusing on the eyepiece/Paracorr combination. I caution any potential buyers to look at their focuser position for the 13 before you buy an 8mm--you will need around a half inch of additional in-focus.

My recommendations:
Use the 13 Ethos as a 2" and use setting 1.
Use the 8 Ethos as a 1.25" and use setting 1 and pull the eyepiece out about 2mm. This will require a LOT of infocusing.

Edited by Starman1 (08/07/08 01:52 AM)


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John Rhodes
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #2564680 - 08/06/08 07:00 PM

Quote:

Ethos Paracorr Settings:
TeleVue's recommended settings are incorrect, according to both my eye and the two excellent calculators on this thread.
<snip>
My recommendations:
Use the 13 Ethos as a 2" and use setting 1.
Use the 8 Ethos as a 1.25" and use setting 1 and pull the eyepiece out about 2mm. This will require a LOT of infocusing.



Wow thats quite a statement...
Let's see : The TV website recommends the #1 setting for the 13 Ethos also,
so how are we incorrect there ?

As for the 8 mm: Your's & our settings are 12 mm apart, which 1.25 adapter are you using on the 8 mm Ethos ?
We recommend the "lower" adapter that comes with the Paracorr.


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Re: List of Paracorr settings for all brands of EP new [Re: John Rhodes]
      #2565417 - 08/07/08 01:27 AM

John,
Yes, the 13Ethos works great at setting 1 (2").
I'm using the standard 1.25" adapter that comes with the Paracorr.
Here's the math:
The focal plane is 0.70" below the shoulder, per TV's chart.
The 1.25" adapter is 0.379" tall (calipers measurement).
That combination results in a focal plane to optimum Paracorr lens distance of 2.76mm too low for the 8mm Ethos when the Paracorr is set to setting 1, that is the 8mm eyepiece needs to go up another 2.76mm to achieve the optimum 55mm distance from focal plane to lens.
Have I missed something?
I could be wrong, but the calculator shows setting 4 would be 12.28mm too low, and that setting 1 is 2.76mm too low.
I'm forgetting something--see below

Edited by Starman1 (08/07/08 01:54 AM)


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #2565437 - 08/07/08 01:51 AM

John, et al.,
My wife just pointed out how much of a bonehead I was. It took her to show me the error in my logic.
Now I eat crow....

The focal plane of the 8mm Ethos is 0.7" below the 2" shoulder.
When I put the eyepiece in the adapter, it automatically raises the eyepiece by the length of the 2" skirt (1.04"). Hence, the focal plane of the eyepiece is now 1.04-0.7 ABOVE the adapter (or 0.34"). So long as I also take into account the thickness of the adapter, the calculator should work fine.

According to the TeleVue website, that means the focal plane is above the reference surface (the bottom of the 2" skirt the eyepiece is resting on).
That means I should be able to plug the 0.34" figure into the calculator and get the proper setting for the Paracorr.

OK. I get setting 3.

It gets setting 4 for the Type 6 Naglers (agreeing with TeleVue), and setting 5 for the 22T4 (again agreeing with TeleVue), and setting 3 for the 17 T4 (same as TeleVue).

But I get setting 3 for the 8 Ethos (no agreement there--TV says 4) and setting 3 for the 16T5 (where TV says 4), but the difference is now 1 setting (0.125" or 3mm).

That says the 8mm Ethos is best used as a 1.25" eyepiece in the Paracorr.

So, John, is my math now better? Or have I overlooked something else?

Edited by Starman1 (08/07/08 01:56 AM)


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #2566327 - 08/07/08 02:06 PM

Plugging the focal plane positions from TeleVue's website into Walt's calculator (and compensating for the skirts on the 12mm T4 and Ethos eyepieces), I get the following optimum(55mm spacing) settings for the Nagler eyepieces(1.25 eyepieces use adapter):
31T5--6 (there is no 6, so use setting 5)
26T5--3.3
22T4--5.2
20T5--1.7
17T4--3.2
16T5--3.7
13T6--4.0
12T4--3.9 (with 1.25" adapter)
11T6--4.0
9T6--4.0
7T6--4.0
5T6--4.0
3.5T6--4.0
2.5T6--4.0
13 Ethos--.8 (as 2")
8 Ethos--4.2 (as 1.25")
Rounded off to the nearest whole number, the settings seem to agree with TeleVue's chart.
It should be noted that TeleVue says +/- 4mm is an acceptable margin for error on the setting. Since the settings on the Paracorr are 3.2mm apart, that means there is quite a bit of leeway in the setting of the Paracorr (i.e. that if optimum is setting 4, good correction can be anywhere from setting 3 to setting 5).

Edited by Starman1 (08/07/08 02:27 PM)


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Zoomit
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #2567428 - 08/07/08 11:02 PM

Quote:


Used as 2" eyepieces in the Paracorr:
13mm Ethos--Setting 1, with the eyepiece pulled out of the Paracorr 1.5mm
8mm Ethos--Setting 1, with the eyepiece pulled out of the Paracorr 12.5mm (not practical unless a 2" skirt is added to the eyepiece)





Don, if you would...can you confirm this is still accurate?


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: Zoomit]
      #2567499 - 08/07/08 11:34 PM

WEll, not quite.
I'm sorry if it wasn't clear.
Close, but not exact.

I was slightly mistaken in how to measure the eyepieces with a skirt.
The Ethos 13, if used as a 2", requires setting 1 (all the way out). That is close to the optimum setting. If used in the 1.25" mode, setting 5.

The Ethos 8mm, if used as a 1.25" eyepiece with the standard Paracorr adapter, requires setting 4. It is not usable in a 2" mode unless a barrel extension is added to the eyepiece, in which case the eyepiece would be pulled out 12.4mm from the Paracorr, with the PC in setting 1. In other words, this eyepiece requires the use of the 1.25" adapter in setting 4. I wouldn't bother to try to use it as a 2" eyepiece in the Paracorr. Just remember that this requires some in-focus movement of the focuser.


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #2621835 - 09/03/08 04:35 PM

Can somebody help me with the Meade 5000 UWA ?
I have 6.7 - 18 - 31mm.
What about Hyperion, e.g 13mm ? Or QX26mm ?
TIA


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Re: List of Paracorr settings for all brands of EP new [Re: Fireball]
      #2622246 - 09/03/08 08:20 PM

It might be helpful to review how to pick a proper setting for the Paracorr:
1) If you have a TeleVue eyepiece, set the Paracorr for that eyepiece (from the TV website) and focus. Remove the eyepiece and insert another. Focus using the tunable top on the Paracorr, not the normal focuser knobs. Note the setting, write it down, because that's the setting for that eyepiece.
2) If you don't have a TeleVue eyepiece, start in setting 1 (tunable top all the way turned out), and put the eyepiece in. Focus. Evaluate star images at edge of field. Still flared in a radial direction slightly? Move Paracorr to setting 2. Refocus. Star images at the edge better or worse? Worse? Setting 1 is your choice. Better? Move Paracorr to setting 3 and focus again. Evaluate stars at the edge. Worse? Go back to setting 2. Better? Continue to setting 4. Etc.
You will find one setting that is the best for that eyepiece. Write it down. Return Paracorr to that setting.
Remove that eyepiece, insert other eyepieces one at a time, and focus using the Paracorr tunable top instead of the focuser. Note the setting for each eyepiece where it is in focus--that's the Paracorr setting for that eyepiece. In this way, you can do a whole collection of eyepieces with experimentation only on the very first eyepiece.


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Robert Provin
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #2678048 - 10/03/08 12:19 PM

Quote:

It might be helpful to review how to pick a proper setting for the Paracorr:
1) If you have a TeleVue eyepiece, set the Paracorr for that eyepiece (from the TV website) and focus. Remove the eyepiece and insert another. Focus using the tunable top on the Paracorr, not the normal focuser knobs. Note the setting, write it down, because that's the setting for that eyepiece.
2) If you don't have a TeleVue eyepiece, start in setting 1 (tunable top all the way turned out), and put the eyepiece in. Focus. Evaluate star images at edge of field. Still flared in a radial direction slightly? Move Paracorr to setting 2. Refocus. Star images at the edge better or worse? Worse? Setting 1 is your choice. Better? Move Paracorr to setting 3 and focus again. Evaluate stars at the edge. Worse? Go back to setting 2. Better? Continue to setting 4. Etc.
You will find one setting that is the best for that eyepiece. Write it down. Return Paracorr to that setting.
Remove that eyepiece, insert other eyepieces one at a time, and focus using the Paracorr tunable top instead of the focuser. Note the setting for each eyepiece where it is in focus--that's the Paracorr setting for that eyepiece. In this way, you can do a whole collection of eyepieces with experimentation only on the very first eyepiece.




Don, your posts here have been very helpful, thank you!

BTW, it was nice meeting you up at Mt. Pinos last weekend.

Robert


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peter k
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #2758267 - 11/18/08 05:48 PM

Quote:

It might be helpful to review how to pick a proper setting for the Paracorr:
1) If you have a TeleVue eyepiece, set the Paracorr for that eyepiece (from the TV website) and focus. Remove the eyepiece and insert another. Focus using the tunable top on the Paracorr, not the normal focuser knobs. Note the setting, write it down, because that's the setting for that eyepiece.
2) If you don't have a TeleVue eyepiece, start in setting 1 (tunable top all the way turned out), and put the eyepiece in. Focus. Evaluate star images at edge of field. Still flared in a radial direction slightly? Move Paracorr to setting 2. Refocus. Star images at the edge better or worse? Worse? Setting 1 is your choice. Better? Move Paracorr to setting 3 and focus again. Evaluate stars at the edge. Worse? Go back to setting 2. Better? Continue to setting 4. Etc.
You will find one setting that is the best for that eyepiece. Write it down. Return Paracorr to that setting.
Remove that eyepiece, insert other eyepieces one at a time, and focus using the Paracorr tunable top instead of the focuser. Note the setting for each eyepiece where it is in focus--that's the Paracorr setting for that eyepiece. In this way, you can do a whole collection of eyepieces with experimentation only on the very first eyepiece.




This is a very useful post--thanks, Don. However, there seems to be something I'm missing. The above quote suggests (to me) that for a given scope there is a single, fixed point of best focus for the Paracorr, and once this is established, focus is obtained for different eyepieces by use of the tunable top, leaving the focuser untouched, regardless of eyepiece. This does not seem consistent with earlier posts, including Don's just a couple up, which states that additional in-focus is needed for the Ethoses. Can someone (Don?) clarify?

Thanks much.


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Re: List of Paracorr settings for all brands of EP new [Re: peter k]
      #2758858 - 11/18/08 11:57 PM

Sure.
There is one distance from the paracorr lens to the eyepiece's focal plane that results in the best coma correction.
But how do you find it?
Answer: correct the coma completely for one eyepiece. You have found that eyepiece's lens-to-focal plane distance.
Insert another eyepiece and focus using the Paracorr top. Note that while doing so, you are effectively moving the eyepiece in and out to adjust the eyepiece position relative to the focal plane of the telescope plus Paracorr. This is really no different than you would do adjusting the focus of the eyepiece in the focuser without the Paracorr, only instead of moving the focuser, you're moving the Paracorr's top.
What it implies, and it would be true, that there is only one position for the focal plane of the telescope, whether the Paracorr is used or not. The Paracorr moves the focal plane position slightly, but the idea is the same as having no Paracorr--you are moving the focal plane of the eyepiece to the focal plane of the scope in order to focus.
The Paracorr does not focus, per se, so you are not focusing the Paracorr, merely putting it into the system to modify the focal plane slightly.

Now, if your eyepiece's focal plane is low in the eyepiece, you will have to move the eyepiece back relative to the Paracorr's lens in order to maintain the correct distance to the lens for best correction. But that means the focal plane of the system is now higher than before. In order to bring the focal plane of the paracorr plus eyepiece to be coincident with the focal plane of the telescope, you will have to move the Paracorr plus eyepiece in to make the focal planes coincident.

So, eyepieces with low focal planes require more out travel with the Paracorr and more inward movement of the focuser.

In a sense, that's no different than an extension tube. Add an extension tube to the focuser, and you will have to move the focuser in to get to focus: eyepiece goes out, focuser goes in.

Hope that makes it clearer.


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interalia
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Re: List of Paracorr settings for all brands of EP new [Re: walt r]
      #2865938 - 01/15/09 01:14 AM Attachment (213 downloads)

A formula I have found useful for finding paracorr settings (in the newer paracorr) when the distance to the focal plane from the eyepiece seat is known is:

8(13/40 - f) or, what is equivalent, 8(0.325 - f)


The attached chart illustrates where the eyepieces in the TeleVue table lie along the range of motion available and the settings best for them. It is from the two constraints that the range of motion is known to be half an inch and that all the eyepieces TeleVue gives settings for must find those settings correctly that the above formula is derived.

Hopefully it may be of some use, and the chart be helpful.


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Re: List of Paracorr settings for all brands of EP new [Re: interalia]
      #2870307 - 01/17/09 02:29 AM

I just got a chance to play with the Paracorr settings for my 8mm and 17mm Hyperions. For both, the best setting seems to be 1.

I was looking not so much for coma correction, which seems to be pretty good at all the settings, but the you can definitely tell a difference in the on-axis star images as you adjust.

I also tried different setings for the Hyperion 31mm Aspheric, and it seems to be giving me the tightest images at setting 5. However, it's not very sensitive to the Paracorr setting, and I might have to try it a few more times to be sure.


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Re: List of Paracorr settings for all brands of EP new [Re: llanitedave]
      #3059078 - 04/22/09 09:09 AM

Reread this thread again. First of all thanks to everyone! It's a must read for using a Paracorr and a fast scope. I've got a few Ethos and the shorter ones I have the 2" barrel extension skirt. Is this going to give me too much distance away from the top lens? Can I use these in setting 1 and get good correction? I'd really like to use them as 2" eyepieces with the skirt if possible. Thanks for your input.

Sean


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Re: List of Paracorr settings for all brands of EP new [Re: phanfave]
      #3059133 - 04/22/09 09:37 AM

Quote:

Reread this thread again. First of all thanks to everyone! It's a must read for using a Paracorr and a fast scope. I've got a few Ethos and the shorter ones I have the 2" barrel extension skirt. Is this going to give me too much distance away from the top lens? Can I use these in setting 1 and get good correction? I'd really like to use them as 2" eyepieces with the skirt if possible. Thanks for your input.

Sean



The 13 and 10 Ethos use setting 1 as a 2" eyepiece, but the 8 and 6mm Ethos use the 1.25" adapter and setting 4. You unfortunately cannot use these two as 2" eyepieces in the Paracorr because the correct position for them would be with the eyepieces pulled 1/2" out of the Paracorr and using setting 1. It's actually more secure to use them as 1.25" eyepieces with the Paracorr.


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phanfave
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #3059212 - 04/22/09 10:29 AM Attachment (160 downloads)

Thanks Don. That makes sense. But it also makes me wonder if the 2" extension skirt would work too since the eyepieces will be further out from the Paracorr compared to using in the 2" mode (or even 1.25" mode with the adapter or the high hat). I picked up the 2" extension this past weekend at NEAF (and they have been slightly redesigned...black anodized now) and have them on the 13,10,8, and 6. I'll get to try them all out tomorrow with the skirt and the Paracorr and will report back here. I'm hoping they work well enough to keep them on.

Here's a pic with the extension on and off:

Edited by phanfave (04/22/09 10:34 AM)


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: phanfave]
      #3059232 - 04/22/09 10:37 AM

Yes, with a 2" extender, you should be able to use the 8 and 6 Ethos as 2" eyepieces in the Paracorr. As I read the calculator, use the paracorr in setting 1, then pull the eyepiece out until the "shoulder" of the upper eyepiece sits 1/2" above the top of the Paracorr(leaving 1/2" of the silver 2" skirt showing).
The 13 and 10 don't need the extender because the length of the extender will prevent them from fully seating in the Paracorr. You would use them without an extender, in 2" mode, at setting 1.
If you are thinking about using the 2" extender to use 2" filters, don't worry--2" filters thread directly to the bottom of the Paracorr. And since the Paracorr doesn't have a "safety undercut", it's easily removable from the focuser to attach a filter to its bottom.

Edited by Starman1 (04/22/09 11:37 AM)


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phanfave
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #3059308 - 04/22/09 10:59 AM

Thanks again! It would have been nice for simplicity sake to use the 13 and 10 with the 2" extension but as you pointed out it's neither necessary nor possible.

Sean


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jonstarrysky
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Re: List of Paracorr settings for all brands of EP new [Re: phanfave]
      #3093189 - 05/08/09 06:39 PM

try using one of these stops to precisely position the Ethos if using the extension barrel:

http://www.cloudynights.com/ubbthreads/attachments/3092105-2009%20Apr%2028%20007%20small.jpg

http://www.agenaastro.com/Baader-Hyperion-2-Finetuning-Stopring-p/paar-bp-hyp-stop.htm

My thinking is as above. E13=#1 (2" mode). E8=#4 (with 2-1.25" adapter). I may leave the paracorr 2-1.25" adapter on my E8 permanently. Simlifies swapping between eg E8, E13, 26T5. Or to use the barrel extension as indiccated.

2" filters at the bottom of the paracorr ? Yes, but youre taking off/ on a mighty train of glass, you dont wanna drop it.


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deSitter
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #3270105 - 08/13/09 10:13 AM

Here's a handy (for me at least) Paracorr trick - defocus so that the shadow of the secondary is clearly visible but not too large - and tune the Paracorr so that the pattern is symmetrical in the out-of-focus center stars as well as the out-of-focus edge stars. Coma will make a lopsided pattern with the shadow close to the inner edge.

-drl


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Re: List of Paracorr settings for all brands of EP new [Re: jonstarrysky]
      #3401958 - 10/21/09 11:18 AM

Anyone have any suggestions for the proper setting on the University Optics 40mm MK-70? I tried this eyepiece for the fist time in my 16" F4.5 dob along with the Paracorr and I was quite happy with the performance. There was still some coma present, but it made a totally un-usable eyepiece in my dob into an eyepiece I will probably use often. The sky background was a bit too gray for my liking in what I would call pretty good skies, but it made a nice view for large objects like the double cluster as it gave a 1.3 deg FOV. The exit pupil is a bit large but I never saw the shadow from the secondary. I found that position 2 seemed to give the best view, any other comments?

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Re: List of Paracorr settings for all brands of EP new [Re: deSitter]
      #3610207 - 02/07/10 10:21 AM

Hi guys,
I just figured something out with the 9 T1 Nagler, and presumably the older 8.8 and 14 uwa eyepieces. Previously I was unable to achieve the best correction using my 9 T1 Nagler in either 1.25 or 2 inch mode. The problem with the 9 T1 is that the it sits down too far in 2 inch mode and up to far in 1.25 inch mode. So, I just bought some 2 inch "parfocaling" rings from scopestuff and put one on my 9 T1 just below the safety undercut. Works perfect on setting 1 along with my 35 and 22 pans.


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Re: List of Paracorr settings for all brands of EP new [Re: Brian Schmidt]
      #3610545 - 02/07/10 01:13 PM

Thanks Brian, thats a good tip. I have the 9 Nagler T1 and just bought the Paracorr. You saved me some grief when my new scope shows up in April.

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DietmarS
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Paracorr and parfocalizing 21mm Ethos doesn't work new [Re: rockethead26]
      #3855091 - 06/09/10 08:13 AM

http://www.cloudynights.com/ubbthreads/showflat.php?Cat=&Board=Eyepieces&Number=3731894

In this thread you will read, that the 21mm Ethos sits about 4mm high on the shoulder of the Paracorr (new or old!).

How can you use parfocalized eyepieces with this?

You would need to have additional 4mm rings to parfocalize for Paracorr use


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: deSitter]
      #3855609 - 06/09/10 01:24 PM

Quote:

Here's a handy (for me at least) Paracorr trick - defocus so that the shadow of the secondary is clearly visible but not too large - and tune the Paracorr so that the pattern is symmetrical in the out-of-focus center stars as well as the out-of-focus edge stars. Coma will make a lopsided pattern with the shadow close to the inner edge.

-drl



Yes.
A defocused star at the edge of the field will not have the shadow centered, but the outer bright pattern in the star should still be round and not oblong.
I used your technique to adjust my 13 Ethos and ended up with the same setting accomplished by looking at the infocus images.
However, your technique doesn't require good seeing.


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roamer
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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #3863048 - 06/13/10 08:22 PM

Quote:

One "relatively" safe means to measure the insertion depth of a late model Visual Paracorr while at its lowest height setting on the tunable top would be to simply place a cotton 'Q'-tip down the side until it rests by gravity on the lens element, and then mark it at the shoulder junction. Then remove it, and stand it up (without any downward force applied), and measure from the table top to the mark on the 'Q'-tip.

CAUTION / WARNING: Again, I warn that I would not wish or intend that anyone scratch a Paracorr in attempting to measure it.




Dang. I must be reading your mind. I did that yesterday to see if an eyepiece would fit and it did.

To anyone: I mainly have a mix of Meade, Televue and Orion Plossl's. Only 2" eyepieces are a MeadeQX 26mm and an Explore Scientific 19mm. I am going to read the Paracorr doco literally and set it to 4 for the plossl's as it say setting 4 for all Plossl's up to 32mm. The 2" eyepieces I am going to have to experiment.

Edited by roamer (06/13/10 08:36 PM)


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rockethead26
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Re: List of Paracorr settings for all brands of EP new [Re: roamer]
      #3903870 - 07/05/10 12:07 PM

My 28 UWAN works best at setting #3.

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Tim A.
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Re: List of Paracorr settings for all brands of EP new [Re: deSitter]
      #4178094 - 11/11/10 02:27 AM

Quote:

Here's a handy (for me at least) Paracorr trick - defocus so that the shadow of the secondary is clearly visible but not too large - and tune the Paracorr so that the pattern is symmetrical in the out-of-focus center stars as well as the out-of-focus edge stars. Coma will make a lopsided pattern with the shadow close to the inner edge.



Brilliant!


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sixela
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #4275891 - 12/28/10 09:03 AM

Quote:

Now your eyepiece's focal plane is low in the eyepiece, you will have to move the eyepiece back relative to the Paracorr's lens in order to maintain the correct distance to the lens for best correction. But that means the focal plane of the system is now higher than before.




Ideally it means it's at the exact same spot despite the different tunable top position.

With ideal positioning, the system focal plane is always at a fixed position with respect to the original focal plane. All the tunable top does is ensure the eyepiece focal plane can be moved there.

The only eyepieces for which in-focus or out-focus is required are those for which the tunable top range is insufficient. So I'm not disagreeing with your post (there are indeed eyepieces like that) but I think I do have to point out that any focuser in- or out-travel is not necessary for most eyepieces (those that have an ideal tunable top position within the real range allowed).

Your own recipe for finding the tunable top position confirms this: once you've set the focuser to the ideal position using a TeleVue eyepiece and the correct tunable top setting, you adjust only the tunable top to find the correct setting for the other eyepieces and you leave the main focuser alone.


Quote:


So, eyepieces with low focal planes require more out travel with the Paracorr and more inward movement of the focuser.




Not unless the focal plane would force an "ideal" setting for the tunable top to be outside the real range.

Consider how the SIPS type 2 Paracorr for the Feathertouch focuser works: it always sits at one spot and you only tune it again if you move the focal plane of the scope (e.g. If you move the primary on its collimation bolts).

Buy the "tunable top" version of that same type 2 Paracorr and set the top correctly, and the lenses will end up at exactly the same position as those from the SIPS version, which entails that the focuser is always racked in the same way. QED.

Note that the SIPS plus Feathertouch focuser leaves only a couple of millimeters when you set it correctly and then focus a 21mm Ethos or 31T5. Fortunately, there are few eyepieces in 2" format that require more in-travel than those, but I have some 1.25" eyepieces that have the focal plane also on the eye side of the shoulder, and some do run out of focuser in-travel unless I use my Borg 1mm profile 2"-1.25" adapter.


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erick
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Re: List of Paracorr settings for all brands of EP new [Re: sixela]
      #4358957 - 02/02/11 06:57 PM

Can anyone advise the setting for the ES 14mm 100 deg?

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Sarkikos
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Re: List of Paracorr settings for all brands of EP new [Re: erick]
      #4381981 - 02/12/11 07:55 PM

After reading this thread, I'm glad I bought a couple TV 25mm Plossls for my binoviewer. I can use one to set my Paracorr correctly. (All the TV Plossls through 32mm have a setting of 4, according to the Televue website.) Then it will be easy to set the Paracorr correctly for my other eyepieces. IMO, any other method seems to be more trouble than it's worth.

My advise is to buy a TV Plossl, the least expensive of the Televue eyepieces. They're even on sale now, or you can get one used. Then you can set your Paracorr and not have to deal with spreadsheets, measure the field stop distance, worry about the height of your 1.25"-2" adapter, or decide whether you can trust the setting advice that someone else gives you.

Get yourself a TV Plossl.

Mike


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star drop
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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #4479351 - 03/28/11 10:57 AM

Explore Scientific 100 eyepiece settings in an adjustable top Paracorr type 1 are:
9 mm setting 2
14 mm setting 2 (actually around 1.75)
20 mm setting 5+ (beyond the range of travel)


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Sarkikos
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Re: List of Paracorr settings for all brands of EP new [Re: star drop]
      #4479391 - 03/28/11 11:19 AM

Thanks, Ted!

I haven't had a chance to take out my scopes for quite awhile. I also have the Paracorr Type 1 with Tunable Top, and both the ES 100deg 9mm and ES 100deg 14mm. Your information will come in handy for me. I was afraid that one or both would not come to optimum correction with the Paracorr Type 1, so this is welcome news.

How did you determine the settings? Did you prime the Paracorr with one of your TV eyepieces?

Mike


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star drop
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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #4479414 - 03/28/11 11:28 AM

Hi Mike,

We primed the Paracorr with my friends 35mm Panoptic eyepiece. Soon I hope to start a new thread about my experience with coma.


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Sarkikos
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Re: List of Paracorr settings for all brands of EP new [Re: star drop]
      #4479448 - 03/28/11 11:42 AM

Very good. As time permits, I'd like to determine the settings for all of my non-TV eyepieces. I'll immediately plug them into my eyepiece spreadsheet, and eventually post them on CN. Not that everyone would be interested in the Paracorr settings for some of my oddball eyepieces, but it is what it is. I'm really surprised this information is not out there somewhere. I certainly haven't been able to find it.

Mike


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thewheel
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Re: List of Paracorr settings for all brands of EP new [Re: star drop]
      #4487227 - 03/31/11 04:20 PM

Hi,
I primed with 11mm TV Plossl and got this:

TV Tunable Top Type 1

Mark Eyepiece
5 = 4.7ES82
4.5 = 6.7ES82
1.75= 9ES100
2.5 = 14ES100
2.75= 28SWA these are the Series 5000 Meade
3 = 34SWA
3 = 40SWA

a little different don't know why , again primed 11mm TVPlossl


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Sarkikos
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Re: List of Paracorr settings for all brands of EP new [Re: thewheel]
      #4487299 - 03/31/11 04:56 PM

Thanks. Yes, your settings and Star Drops differ a bit. I don't know exactly why they should vary. But both of these eyepieces seem to have a setting around 2. Maybe the fractional differences don't really make that much of a difference. A distinction without a difference?

9ES100: Star Drop 2, thewheel 1.75
14ES100: Star Drop 2 (1.75), thewheel 2.5

I'm curious to see the values I get when I have a break in the weather here.

Mike


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star drop
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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #4487861 - 03/31/11 08:43 PM

Might the variation be due to Televue's rounding out of their prescribed settings? We each primed with different Televue eyepieces.

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Sarkikos
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Re: List of Paracorr settings for all brands of EP new [Re: star drop]
      #4488214 - 03/31/11 11:37 PM

That's a possibility. Televue always lists the settings as whole numbers. The way I understand it, the setting is dependent on the offset between the Paracorr lens assembly and the eyepiece's field stop, which should always be 55mm. Would that distance always be exactly at one of the Tunable Top settings? Unlikely.

Also, is the field stop of every TV Plossl, or every Radian, for instance, always at the exact same distance below the shoulder of the eyepiece barrel as the other eyepieces in that series? If they're supposed to be parfocal, I guess that could be true.

Mike


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star drop
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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #4512547 - 04/12/11 01:34 AM

Priming a type 1 Paracorr with a 35mm Panoptic the setting for: 30mm Meade UWA is 1.5

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star drop
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Re: List of Paracorr settings for all brands of EP new [Re: star drop]
      #4545004 - 04/26/11 09:39 AM

Perhaps this information from the Televue eyepiece specifications page is relevant.

Panoptic field stops with respect to reference surface:

41mm .27
35mm .17
27mm .29
24mm .25
19mm .25

Plossl field stops with respect to reference surface:

8mm through 32mm .25

The 35mm Panoptic's value is the farthest from the approximate average value of around .25 and so it might not be the optimum eyepiece to use as a primer. If one takes my value for the 14mm ES 100 and multiplies it by .25/.17 the resulting value is very close to the value arrived upon by thewheel.
1.75 x .25/.17 = 2.57
If I ever get another clear night I will try priming the Paracorr with a few other Televue eyepieces.


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Re: List of Paracorr settings for all brands of EP new [Re: walt r]
      #4555061 - 05/01/11 12:27 PM

Is there a list of Parracorr Type 2 Eyepiece settings for NON-Televue eyepiecs. I don't use my Parracorr as much as I should because I don't have the time to figure out all the settings for each eyepiece.

The only Televue eyepieces I hae are 10mm Ethos (at top most setting), 3.7mm Ethos (also top most setting), and 24mm Panoptic (uses only for binoviewing w/o Parracorr).

Currently the single eyepiece I use most is the Explore Scientific 20mm 100 AFOV at setting C.


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: faackanders2]
      #4555195 - 05/01/11 01:48 PM

Quote:

Is there a list of Parracorr Type 2 Eyepiece settings for NON-Televue eyepiecs. I don't use my Parracorr as much as I should because I don't have the time to figure out all the settings for each eyepiece.

The only Televue eyepieces I hae are 10mm Ethos (at top most setting), 3.7mm Ethos (also top most setting), and 24mm Panoptic (uses only for binoviewing w/o Parracorr).

Currently the single eyepiece I use most is the Explore Scientific 20mm 100 AFOV at setting C.




Put the 10 Ethos in at setting A (highest setting). Focus.
Insert the 20 ES and focus using the tunable top, not the focuser knob. Mark down the setting of the Paracorr. That will be the setting you tune to before you insert the 20 ES the next time.

You only focus using the tunable top to find the proper setting for the non-TeleVue eyepiece. In the future, you set the tunable top to the correct setting, insert the eyepiece and focus using the focuser.

In this same way, you can find the correct settings for an entire collection. Note that some 2"/1.25" hybrid eyepieces can not be optimized unless used in the 1.25" adapter: Ethos 8, Ethos 6, and others.

Edited by Starman1 (05/01/11 01:49 PM)


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bgavin
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #4555397 - 05/01/11 04:01 PM

Don, I was thinking about this process.

Does this take into account the varying amount of in-focus required between dissimilar EPs?

I have the Type 2, not used it yet.
I figure I can calibrate it with either the Radian 14, or the Panoptic 27.

It just seems to me that an EP with a different point of focus would require prime focus set first, then coma adjustment with the tunable top.

Or... I'm not yet understanding how it works..


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: bgavin]
      #4555505 - 05/01/11 05:28 PM

Quote:

Don, I was thinking about this process.

Does this take into account the varying amount of in-focus required between dissimilar EPs?

I have the Type 2, not used it yet.
I figure I can calibrate it with either the Radian 14, or the Panoptic 27.

It just seems to me that an EP with a different point of focus would require prime focus set first, then coma adjustment with the tunable top.

Or... I'm not yet understanding how it works..



The Paracorr's lens sits in the scope's light cone at a certain, distinctive, position, relative to the focal plane for it to correct coma correctly.

Likewise, the distance between the focal plane of the eyepiece and the Paracorr lens has to be a certain distance for the eyepiece to be able to focus on the coma-corrected focal plane of the scope + Paracorr.

That's why there can be a new focuser that incorporates a Paracorr lens. The lens is fixed relative to the telescope's light cone, and the eyepiece is adjusted in and out (using the focuser) until it comes to focus.

This is essentially what happens when you set the Paracorr for a known eyepiece and focus. You're putting the Paracorr at the correct distance from the focus of the scope and adjusting the tunable top to put that eyepiece at the right distance from the lens. When you adjust the tunable top (which has 7/8" of an inch of adjustment not counting the extra height of the 1.25" adapter), you are essentially doing what the person with the paracorr-in-focuser is doing, which is adjusting the distance between the focal plane of the eyepiece and the lens of the Paracorr.

Now, not every eyepiece will fall into the range of motion on the Paracorr's tunable top. Some 2" eyepieces might need an extension tube to get them far enough away from the lens (as would, for instance, an 8 Ethos used as a 2" eyepiece), and, conceivably, there could be an eyepiece that needed to get closer than the in-most setting.

But the range should be sufficient for most eyepieces.

Since focusing with an eyepiece of known setting has placed the Paracorr lens relative to the focus of the scope, you can dial in any other eyepiece by simply adjusting the tunable top to focus, leaving the Paracorr where it is by not using the focuser (which would move the Paracorr's lenses relative to the scope). So fixing the Paracorr lens using a known eyepiece and then focusing a new eyepiece by using the tunable top simply finds that new eyepiece's correct Paracorr setting, i.e. adjusts the correct distance from eyepiece focal plane to Paracorr lens.


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Re: List of Paracorr settings for all brands of EP new [Re: Lawrence Sayre]
      #4563386 - 05/05/11 01:03 PM

so if i have this right, you focus your first2 inch eye piece in the paracorr, adjust settings until best correction, re focus, then switch eyepieces and only adjust the paracorr. then for 1.25 eyepieces you start from the beginning again and do the same thing. i just got my paracorr and haven't been able to try it yet. i have all but one of the ES 82s so i will list them when i get them right. they are well corrected at f4.9 with just minor coma at the edge so i am expecting a lot from this paracorr. if they are not coma free, i will be disappointed.

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Re: List of Paracorr settings for all brands of EP new [Re: Sean Puett]
      #4563460 - 05/05/11 01:45 PM

My understanding is that it does not matter if you prime the Paracorr with a 1.25" Televue or a 2" Televue, as long as you know the prescribed setting for the TV eyepiece. For a 1.25" TV eyepiece, I would use the 1.25"-2" adapter that came with the Paracorr. What you are doing is finding the correct Paracorr lens cell position within the focuser, given the setting for a TV eyepiece per Televue. Then you keep the focuser at that position and use the Tunable Top to determine the best setting for a nonTV eyepiece by seeing where it comes to best focus.

It doesn't matter if you are finding the setting for a 2" or 1.25" nonTV eyepiece. Just keep track of the specific 1.25"-2" adapter or 2" extension or spacing ring or visual back or whatever that you are using when you focus the Tunable Top to determine the setting for that eyepiece. That way you can be sure to set up the eyepiece correctly the next time you insert it in the Paracorr. Some trial and error is obviously involved, more for some eyepieces than for others.

Mike


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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #4563537 - 05/05/11 02:29 PM

thanks. this was my first TV purchase and i like the feel/build quality. i may even buy an ethos when they release the 120deg afov eyepieces. :-)

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Re: List of Paracorr settings for all brands of EP new [Re: Sean Puett]
      #4649026 - 06/20/11 12:14 PM

Televue 32mm Widefield setting 1.

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Re: List of Paracorr settings for all brands of EP new [Re: star drop]
      #4649204 - 06/20/11 01:57 PM

I've been using the Type-II a lot the last couple of weeks.
One of the startling things is how MUCH change occurs with small movements of the tunable top.

Q: is there any merit in using a TV eyepiece with a focal length closest to the EP under test?

For example, I want to adjust for an ES82 14mm.
I can use a Radian 14mm or a Panoptic 27mm.

Logic tells me to use the Radian for the ES14, and use the Pan27 to calibrate for my 27mm Flat Field, etc.


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Re: List of Paracorr settings for all brands of EP new [Re: bgavin]
      #4649253 - 06/20/11 02:23 PM

I have no choice. My TV Plossl 25mm is the only TV eyepiece that I own. That will be my priming eyepiece.

I've been waiting for a night around Full Moon to collect the settings for my other eyepieces, or at least for the ones I use the most. I can do that beside my house here in red zone suburbia. But the weather hasn't cooperated. I don't want to waste a night at my dark site fiddling with equipment settings. That would not make sense, IMHO. (Though I've seen others do it many times. )

I don't even want to fool around with gathering techie gizmo settings if the Moon's between New and Full, or there's a planet up that I can observe. I like to observe the Moon, planets and DSO. And taking into account the general bad weather this spring, that does narrow down my chances of getting any settings any time soon.

I guess I'll just have to sacrifice a perfectly good observing night on nerdy techie gizmo stuff.


Mike


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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #4649263 - 06/20/11 02:29 PM

Mike, I've been watching around for a 20mm TV Plossl, just for fun. EdZ is seriously impressed, and I kinda wanted one anyway..

My Type-II is mostly living in my scope full time.
However... the TV 1.8x Barlow is not compatible due to physical contact.
I'm not enamored of Barlows/Powermates (yet), so no big deal.

I'm stoked over putting a single 2" filter in the Type-II for lunar. Geez Louise.. does that get bright in 10".
I have the variable polarizer, now thinking a fixed ND might be more useful, less fiddling.

My Type-II was purchased to do double duty with System 2.4 imaging screwed directly to the Paracorr optics.
I'm glad it was on sale... pricey.


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Re: List of Paracorr settings for all brands of EP new [Re: bgavin]
      #4649301 - 06/20/11 02:52 PM

Bruce,

Quote:

Mike, I've been watching around for a 20mm TV Plossl, just for fun. EdZ is seriously impressed, and I kinda wanted one anyway..




I sorta wished you'd told me that in a PM ...

Quote:

My Type-II is mostly living in my scope full time. However... the TV 1.8x Barlow is not compatible due to physical contact.
I'm not enamored of Barlows/Powermates (yet), so no big deal.




I have a series of Barlows, but I hardly use them anymore. If I binoview lunar/planets, I screw on a 1.9x or 3x OCS so the eyepieces will come to focus. Without the binoviewer I just slip in a simple Ortho, RKE or Brandon. Particulary for faint fuzzies, I try to avoid adding to the glass in the path, though the Paracorr will immediately contradict that principle, of course. On the other hand, I think I will experiment with my ES 100 deg 9mm + 1.5x lens assembly + Paracorr, if that is possible. That combo, if it works, would be particularly good for bright planets or the Moon.

Mike


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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #4649325 - 06/20/11 03:06 PM

Mike,
I found the optimum sequence to be:
eyepiece>>Paracorr>>Barlow or PowerMate.
It would seem to me that if a barlow was in between the eyepiece and Paracorr that the proper setting of the Paracorr top would have to be redetermined, and might exceed the range of adjustment.
Whereas if the barlow is in front of the Paracorr, refocusing would be necessary, but probably not the eyepiece--Paracorr setting.

Edited by Starman1 (06/20/11 03:08 PM)


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #4649444 - 06/20/11 04:23 PM

A bit OT, but my best use for a 2.5x Powermate is prime focus DSLR photography.
The Type-II provides is a direct attach for unmagnified prime focus using a TV T-ring plus Nikon T-adapter.

My initial testing of TV 1.8x and 2.5x shows image degradation, Type-II not installed.

To do the Powermate + Paracorr thing, I'd need a 2" PowerMate ($$) so I could be disappointed on a more expensive scale.


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #4649712 - 06/20/11 06:59 PM

Don,

Quote:

Mike,
I found the optimum sequence to be:
eyepiece>>Paracorr>>Barlow or PowerMate.
It would seem to me that if a barlow was in between the eyepiece and Paracorr that the proper setting of the Paracorr top would have to be redetermined, and might exceed the range of adjustment.
Whereas if the barlow is in front of the Paracorr, refocusing would be necessary, but probably not the eyepiece--Paracorr setting.




Yes, that sounds right. I'll have to remember to try the setup that way. In fact, I think you mentioned this in a thread, and probably to me! So many gizmos, so little time...

I think the best method for my purposes would be to screw a 2" Barlow lens assembly onto the end of the Paracorr, insert the TV Plossl 25mm, tune it to setting "4", and find best focus using the focuser. Next lock the focuser at that position and replace the TV eyepiece with the ES 100 9mm (or another eyepiece). Then use the tunable top to find best focus for that eyepiece. There may be a fudge factor involved because of the height of the 1.25-2" adapter, but this should get me close.

There is a chance a particular eyepiece will not come to focus this way, but it's worth a try. I have two different visual backs (or whatever) to attach to the top of the focuser - one very short, one tall. One or the other might work.

Mike


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Re: List of Paracorr settings for all brands of EP new [Re: bgavin]
      #4649726 - 06/20/11 07:09 PM

Bruce,

Quote:

I'm stoked over putting a single 2" filter in the Type-II for lunar. Geez Louise.. does that get bright in 10".
I have the variable polarizer, now thinking a fixed ND might be more useful, less fiddling.

My Type-II was purchased to do double duty with System 2.4 imaging screwed directly to the Paracorr optics.
I'm glad it was on sale... pricey.




If you want to use the VP, you could screw one filter onto the Paracorr and put the other on the end of your eyepiece. Then just turn the eyepiece to adjust the brightness of the image. Make sure the filter isn't deep enough to scratch the top lens of the Paracorr, though.

I've tried VPs. I didn't like them. They seemed to degrade the image more than a single filter, such as an ND. For my 10" Newt, I like to use a 47 Violet or a 25 Red. Also, an apodizing mask will cut down the brightness and make eye floaters much less noticeable. But it's anathema to observe the Moon with an apodizing mask, so forget I even mentioned it.


Mike


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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #4649964 - 06/20/11 09:14 PM

Quote:

If you want to use the VP, you could screw one filter onto the Paracorr and put the other on the end of your eyepiece. Then just turn the eyepiece to adjust the brightness of the image.



What a grand idea.

I have two sets of VP, 1.25" and 2". Mix 'n match would let this work on both EP sizes.

The Paracorr lets me place a 2" filter in the bottom, which makes changing EP a fast and easy process UHC filters, etc.


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Re: List of Paracorr settings for all brands of EP new [Re: bgavin]
      #4650018 - 06/20/11 09:54 PM

Bruce,

Quote:

I have two sets of VP, 1.25" and 2". Mix 'n match would let this work on both EP sizes.




Yep, that would do the trick. I might take my VPs out and try them again when I get around to acquiring all those Paracorr settings. The Moon close to Full would make a nice easy target.

What I will probably do, also, is screw my 2" Semi-Apo filter onto the Paracorr and try different color filters on the eyepiece while I'm looking at Jupiter when it's better positioned. I've found that a Semi-Apo or Moon & SkyGlow combined with various color filters will improve contrast and bring out various features when observing bright planets. I'd rather use a filter wheel, but I don't have much hope of that working with a Paracorr.

Mike


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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #4650264 - 06/21/11 12:01 AM

OPT has a nice deal going on the Televue TRG-1072 t-ring adapter for the Type-II Paracorr.
I try to support our sponsor, but they are $10 higher for the shipped item.

This adapter screws directly to the Type-II optical assembly when the tunable top is removed. It presents a standard T-Ring thread which mates with my Nikon T-adapter.

As it turns out, the Nikon sensor distance + T-ring + TRG-1072 is almost the perfect back focus distance.
The native prime focus (no Powermate) calculates as pretty close to the FOV seen by the Pan27 on my scope.

I already have the Powermate PTR-1250 adapter that mates the 1.25" Powermates to standard t-adapters.
This is surprising high magnification, so I'm thinking the unamplified prime focus might be more useful.
Either way, I get the full benefit of the Type-II optics for the final image.

Overall, the Type-II really impresses me with its very high quality construction and workmanship.
The TV gear is definitely worth the extra $$.

I run the Pan27 at the recommended setting, and the views are just fabulous.. all the way to the edge.


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Re: List of Paracorr settings for all brands of EP new [Re: bgavin]
      #4653092 - 06/22/11 03:48 PM

I posted this to a thread in the reflector section but I will repeat it here as this seems a more appropriate place.

I have seen a few posts from time to time asking what the Paracorr setting is for a particular eyepiece, and of course there is the lead post at the top of this section on Paracorr settings for different brands of eyepieces. However, the Paracorrs are easy to setup or calibrate on any scope and you can determine the correct setting for any eyepiece easily yourself - and you do not need a Televue eyepiece to do it.

The Paracorr is designed to be placed in the scope's light path at a position that achieves a specific distance from the Paracorr's last lens vertex to the focal plane; this is often called bfl or back focal length. The Paracorr is setup in your scope just as if you were going to do imaging with a camera or CCD; instead of placing a sensor at the focal plane you simply look at the focal plane with an eyepiece.

This specific distance is defined in the Televue literature several places. It is listed as 55 or 56 mm +/-4 mm for the PC1 and 55 or 57mm for the PC2. The tolerance of +/- 4 mm is generous so lets just say its 56 mm (2.20").

So, find a plastic soda straw or swizzel stick and make a mark on the side of the straw with a pen or sharpie 56mm (2.20") from one end. Loosen the hold down screw for the tunable top and place the PC on a table with its axis vertical. Carefully place the end of the straw or stick into the PC until the end just touches the center of the last lens. Adjust the tunable top until its top surface is even with the mark that you made on the straw. A flat item, such as a short plastic ruler laid across the top of the tunable top makes this easy.

Your PC is now calibrated to have the focal plane coincident with the top of the tunable top. Now all you do is place a strip of Scotch Magic tape (or other translucent cellophane tape) across the top of the tunable top; make sure the tape is taught, not sagging across the top. Put the PC in your scope, line up on a bright star and move the focuser until the star is sharply focused on the tape. Then, lock the focuser, or be sure to not touch the focuser knob.

You are all set to find the PC setting for any eyepiece - just put in your eyepiece and adjust the tunable top (not the focuser knob) until a star is focussed and record the setting. Repeat for any other eyepieces in question. Keep in mind that there is no guarantee that the PC will be able to focus your eyepiece, especially the older PC1. Many eyepieces (especially 1.25" ones) need more "in" travel to be properly set; you may need to find a different 2" to 1.25" adapter than the one that came with the PC1 with a thinner flange to allow the eyepiece to go further into the PC. I had to machine a special thin flange adapter to allow several of my eyepieces to focus.

But let's go back a few steps and look at the position of the tunable top after we calibrated it with our plastic straw "gauge". You will likely find that the PC1 tunable top is set right at or very close to the middle (3) mark; if you did the calibration on a PC2 you will find that the tunable top is set at the middle or "E" position. This is no coincidence. The older PC1 literature did not say much but the new PC2 literature shows clearly that the focal plane of the telescope is located at the top of the tunable top when at the "E" position without the 1.25" adapter, and the focal plane is located at the top of the inserted 1.25" adapter when at the "A" position.

So you do not even have to go through the "calibration" steps using the plastic straw we discussed above, unless you just want to prove it to yourself. Simply set the PC as follows:

PC1 - "3" setting (middle position)
PC2 - "E" setting for 2" mode
PC2 - "A" setting for 1 1/4" mode

Put the magic tape across the top, focus a star on the tape and you are ready to go as described above. Use your straw or stick to enjoy your favorite beverage....

Clear skies,

Ron


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Re: List of Paracorr settings for all brands of EP new [Re: rprice]
      #4659559 - 06/26/11 11:42 AM

Ron,

Thanks for the info. I have the PC1. If I were to use setting "3" and a piece of clear tape to set the focal position of my scope, should I take off the 1.25"-2" adapter? Should I place the tape directly over the top of the Paracorr without the adapter? That's what I would think, but I like to remove all ambiguity.

Also, if anyone were to go through the calibration process, they should use a Q-tip or something similar that has a soft end rather than a straw, to avoid scratching the Paracor lens.

It is true that there are many 1.25" eyepieces that will not come to focus in the PC1. I just tried to determine the Paracorr settings for eleven 1.25" eyepieces. Seven out of eleven eyepieces would not come to focus. There was not enough in-focus. I was using the TV 1.25"-2" adapter that comes with the PC1. I might try other adapters.

I'm definitely not buying the PC2. Forgetaboutit. I'm either going to make the PC1 work for me or I'm going to sell it. So far this gizmo is not worth all the trouble.

Mike


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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #4659599 - 06/26/11 11:54 AM

Last night I went to a dark site. The predictions on three different websites were for a clear sky. Wrong! The sky was cloudy all night. But I could see some bright stars. So the night would not be a total waste, I took out my PC1 and started determining settings for some of my eyepieces. For all these eyepieces I used the 1.25"-2" adapter supplied with the PC1.

Here are the results:

ES 4.7 82deg: 5 (This matches thewheel's finding.)

Meade 5k UWA 6.7: Not enough in focus

Vixen LVW 8: Not enough in focus

AT Paradigm Dual ED 12: Not enough in focus

ES 14 82deg: 5

Faworski Super Abbe Ortho 16.8: Not enough in focus

Orion Epic ED-2 22: Not enough in focus

Meade 5k SWA 24: Not enough in focus

UO Abbe Ortho 25: 2.75

Brandon 32mm: 3.75

Baader Mark-II Zoom (1.25" mode): Not enough in focus

Mike


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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #4659806 - 06/26/11 01:49 PM

The Paracorr 2/1.25" adapter has a thick flange. I have an adapter that came with my Tectron telescope that has a ~1/32" flange. Using something like that might give you ~3/8" more in focus.

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Re: List of Paracorr settings for all brands of EP new [Re: star drop]
      #4659867 - 06/26/11 02:24 PM

And AstroSystems has an adapter on their website that actually allows the eyepiece to drop BELOW the lip by 1/2".
So, depending on which adapter is used, you should be able to achieve enough inward movement of the tunable top for most 1.25" eyepieces.
2" eyepieces? Well, it depends. I think that the 31 Nagler and 21 and 17 Ethos eyepieces, which necessitate a setting lower than the lowest setting on the Paracorr 1, were, in addition to the shorter f/ratios becoming more common, a reason for the creation of the Paracorr 2, which has lower settings than the Paracorr 1.
For 1.25" eyepieces, though, various adapters seem to suffice.
Most 1.25" eyepieces use setting 4, some use setting 5, but if the tunable top needs to go lower than setting 5, a shorter adapter is all you can do. And if that's still not perfect, then use the PC on setting 5. Like the 31 Nagler, it's not going to be perfect, but it will be a lot better than no Paracorr at all.


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #4660247 - 06/26/11 06:33 PM

I have several 1.25"-2" adapters here that I could use. I'll compare them with the TV adapter. Just by a quick glance, I know that my Orion "Precision Centering Adapter" is a little lower than the TV one.

An adapter that allows the eyepiece to drop below the lip by 1/2" seems to be the way to go. I've seen these online, thought about buying one. This will be a good time to do it. I did want to be able to use a wide variety of 1.25" eyepieces with the Paracorr for observing planets. Hopefully the Paracorr will clean up the coma enough to improve my observations of planets even more than I've already been able to do up to now. (Too bad the Paracorr can't be used with a binoviewer.)

Mike


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #4660376 - 06/26/11 07:53 PM

Don,

Quote:

And AstroSystems has an adapter on their website that actually allows the eyepiece to drop BELOW the lip by 1/2".




I found two of these low profile adapters. One is on the AstroSystems website. They say that their adapter will "lower the profile of your 1.25" eyepiece another 0.5" below the drawtube." $29 + shipping.

Ultra low Eyepiece Adapter - 2" to 1.25"

The other low profile adapter is advertised on the ScopeStuff website. According to ScopeStuff, their "Negative Profile Eyepiece Adapter allows the eyepiece to be inset over 3/4" more than a low profile adapter." $39 including shipping.

Negative Profile Eyepiece Adapter, 1.25" to 2"

I wonder if they are the same adapter, or are essentially the same? I'm tempted to order the ScopeStuff adapter for the extra 1/4" eyepiece inset. However, judging by the two descriptions, AstroSystems and ScopeStuff might measure the amount of extra inset in different ways, so that actually they both may have the same inset?

I'm tempted to go with the ScopeStuff adapter.

Mike


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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #4660400 - 06/26/11 08:11 PM

Mike,
I think they are essentially the same adapter. One has a 1/2" drop from the lip, and the other has a 3/4" drop from a low-profile adapter (which would typically have about a 1/4" lip).
One caveat: these provide the full drop only with small diameter 1.25" eyepieces. Many 1.25" eyepieces today don't even fit into the recess because the upper sections of the eyepieces are too large. Because there is no screw above the top of the focuser, the upper lip is as thin as they get, so even without fitting into the recess, the adapter is still thinner than most adapters. You'll gain a setting, maybe two, on the Paracorr even if the eyepiece doesn't fit in the recess.


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #4660478 - 06/26/11 09:07 PM

Don,

My simple, old-school eyepieces such as the Orthos, Brandons, RKEs and Plossls should have no problem fitting into the "well" in the adapter. There may be a problem with already low eye relief getting even lower. But it's definitely worth $30 or so if it will allow many of my 1.25" eyepieces to perform better with the Paracorr.

Mike


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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #4661509 - 06/27/11 02:04 PM

Mike,

Quote:

Thanks for the info. I have the PC1. If I were to use setting "3" and a piece of clear tape to set the focal position of my scope, should I take off the 1.25"-2" adapter? Should I place the tape directly over the top of the Paracorr without the adapter? That's what I would think, but I like to remove all ambiguity.




Yes, when using setting 3 the tape should be placed across the top of the PC1 without the 1.25" adapter.

Quote:

I'm definitely not buying the PC2. Forgetaboutit. I'm either going to make the PC1 work for me or I'm going to sell it. So far this gizmo is not worth all the trouble.






I will agree with you on this point. My scope is a 24" f/3.65 and I recently purchased a Paracorr2 to see how it compared to the PC1. The short answer is there is no discernable difference between the two Paracorr versions from a visual observing standpoint for my scope. I am sure that if I was CCD imaging over a large field of view I would see a slight improvement in the quality of the star images at the edge of my image with the PC2, but visually there is no difference.

I compared the PC1 and PC2 using a 22NT4 eyepiece in my scope, going back and forth several times carefully evaluating the quality of a star image at center, halfway out, 3/4 of the way from center to edge and right at the field stop. There was virtually no difference between the two Paracorrs.

There have been a few comments going around that the Paracorr2 has better coatings than the somewhat older PC2, so I evaluated limiting magnitude between the two PCs. I looked at several star fields, going back and forth between the PC1 and PC2, and I could see no difference.

In all honesty, I really did not expect to see a difference between the two Paracorrs. If you carefully examine the performance graphs provided by Televue for the PC1 and PC2, while the PC2 performance is completely diffraction limited for my f/3.65 scope, even the older PC1 brings the off-axis spot size for a star at the edge of the 22NT4 field stop within a factor of 2 or so of diffraction limited. This is still a very tight image and its defects would not be visible at the very low power of the 22NT4; you need at least 25 to 30X per inch to start seeing details of the diffraction disc and the 22NT4 is only giving me 5X per inch.

So what's going on?? Well, in a nutshell, coma is not the problem; it is off-axis astigmatism (and a small amount of field curvature) in the long focal length, ultra-wide angle eyepieces that I use in my scope. Many people state that they see lots of coma in their fast Newtonian reflector when they do not use a Paracorr, but I submit they are not seeing coma at all; they are seeing predominantly off-axis astigmatism generated by the eyepiece due to the fast f/#. This was pointed out over 20 years ago in the book Telescope Optics by Rutten and Van Venrooij, and we all know that Newtonians have gotten much faster than the f/5 versions that were evaluated in that book.

Star images appear better when you add the Paracorr not because you have eliminated coma, but because you have slowed the f/# down by 15% reducing the off-axis astigmatism produced by the eyepiece. In my case it changes my f/3.65 scope to an f/4.2 scope. This 15% change may not sound like much, but I believe that the off-axis astigmatism generated by the eyepiece is inversely proportional to the f/# squared, so this would be a 32% difference.

This new generation of ultra-fast Newts is really catching on and I believe rightly so. I love standing on the ground half the time and only going up two short steps to look at an object near the zenith. And my scope is very compact and easy to move in and out of the garage. You just need to be aware that even the best available long focal length (> 20mm), wide angle (>65 degrees AFOV) eyepieces are going to have poor edge performance, Paracorr not withstanding. Shorter focal length / higher power eyepieces work much better because they do not exhibit near the off-axis astigmatism; Pentax XW's 10mm and shorter, Radians 14mm and shorter work quite well at f/3.65 (without PC) with only minor defects in images near the field stop. I am anxiously awaiting the new Delos line from Televue, hoping that they will perform well at these fast f/#s.

Sorry for the long winded reply.

Ron


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Re: List of Paracorr settings for all brands of EP new [Re: rprice]
      #4661598 - 06/27/11 02:51 PM

Ron,

Thanks for the "long winded reply." I am glad to hear that apparently the only observable difference between the PC1 and PC2 is the wider range of in-focus settings for the PC2. That will probably be particulary true in my Newts, which are all f/4.8 and slower. Hopefully I can work around the not-enough-in-focus problem in my PC1 by using the negative profile adapter I ordered last night.

Unless the observer is experienced at evaluating eyepieces, it can be difficult to distinguish among coma, astigmatism, field curvature, etc. I don't presume to have the level of expertise as some of the experts on CN. If the image looks better to my eyes, I am happy. Also it should be kept in mind that at low power, the observer may start seeing whole eye astigmatism, which we cannot blame on the scope, the eyepiece or the Paracorr. FWIW, I've noticed that sometimes SCT users, who might not be accustomed to wide exit pupils, are surprised at the level of astigmatism that can be seen in Newts at low power, whether from eyepiece or eyeball or both.

Mike


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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #4661659 - 06/27/11 03:32 PM

I evaluated both older and newer Paracorrs in my f/5 scope.
My findings were totally expected:

31 Nagler and 21 Ethos had improved edge-of-field stars in the Type 2 because of the lower setting possible on the Type 2. The Type 1's lowest setting wasn't low enough for optimum edge correction.

I saw no other obvious differences (I didn't expect to at f/5 because f/5 was fully-corrected by the Type 1 Paracorr).

Whereas Ron is mostly right about many inexpensive 2" eyepieces and astigmatism, the Nagler he compared, and my Ethos eyepiece set, has no edge-of-field astigmatism. The design is free from that problem down to f/4.

In my case, f/5 is not short enough to induce any form of astigmatism at the edge of the field in the Ethos eyepieces, yet, without the Paracorr, all my eyepieces display what is, to my eye, horrible coma. The star images are probably 10X as long, radially, as they are circumferentially. With the Paracorr, the stars at the edge are small points.

You see, coma is a linear problem that starts in the center and gradually increases toward the edge. The linear size of a comatic star depends solely on the distance from the center of the focal plane of the scope.
But the apparent size of the comatic star image depends on magnification.

So, for example, a 100 degree 21mm eyepiece will have the same magnification as a 21mm 50 degree eyepiece, but because the radius of the field will be twice as large in the 100 degree eyepiece as in the 50 degree eyepiece, the linear AND apparent size of the comatic star images at the edge of the field in the 100 degree eyepiece will be twice as big, and appear worse.

Double the magnification but keep the apparent fields the same, and the 50 degree eyepiece will see a comatic star image at the edge which has half the linear size, but at twice the magnification. Hence, the comatic images at the edge will appear the same as at half the power. The same is true of the 100 degree eyepiece. The comatic star images appear twice as wide as the 50 degree eyepiece, and it displays the same difference with the 50 degree eyepiece as at the lower power.

So the visibility of coma is related to the apparent field of the eyepiece: Wider = More coma at the edge.

And if the eyepiece is fully corrected for astigmatism at the f/ratio you are using, you will see coma, and perhaps de-focusing caused by field curvature, at the edge, but not astigmatism. Of course, field curvature, which might cause the stars to bloat, may make coma appear worse than it is.
I had an eyepiece that had horrible coma at the edge that the Paracorr corrected, leaving small, out-of-focus, star images due to that eyepiece's inherent field curvature. I dealt with it by focusing at the 50% field point and letting my vision correct for the center and edge. That worked because it was a low-power eyepiece.

I found myself surprised at how bad coma actually appeared at f/5. I thought, and still think, that a coma corrector is essential at f/5 to produce good star images over the entire field of view. Looking at the correction charts on the TeleVue site corroborates what I see.

But Ron is right that if the eyepiece has substantial astigmatism, correcting the coma will not be sufficient to correct the star images at the edge of the field. If you're trying to correct an Erfle eyepiece, for instance, the star images at the edge after coma correction will still appear non-stellar.
But, the best-corrected eyepieces of today will have star images tight enough at the edge, if corrected by a coma corrector, to see a globular cluster exit the field with the core still completely resolved. I am certain of that--I've seen M15 exit the edge of my 13 Ethos with the core still resolved into tiny pinpoint star images.
The correction at f/4 won't be as perfect, but the difference will not be that bad. The coma-corrected f/4's star images are still WAY better than the non-coma-corrected f/5's.


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Re: List of Paracorr settings for all brands of EP new [Re: bgavin]
      #4661852 - 06/27/11 05:55 PM

Don,

Quote:

Whereas Ron is mostly right about many inexpensive 2" eyepieces and astigmatism, the Nagler he compared, and my Ethos eyepiece set, has no edge-of-field astigmatism. The design is free from that problem down to f/4.






That is an interesting statement; the word "no" is pretty absolute. I would appreciate your referring me to where this is stated in Televue literature or elsewhere.


Quote:

In my case, f/5 is not short enough to induce any form of astigmatism at the edge of the field in the Ethos eyepieces, yet, without the Paracorr, all my eyepieces display what is, to my eye, horrible coma. The star images are probably 10X as long, radially, as they are circumferentially. With the Paracorr, the stars at the edge are small points.






What you are describing does not sound like coma; the comatic blur does not have a 10 to 1 aspect ratio like that. If you place a bright star at the edge of the field and focus in and out, you will probably find that the very long radial image will cross over into a circumferential one - this is what I see at the edge of the field with long focal length /wide field eyepieces and it is astigmatism, not coma.

Your description of coma as varying linearly with field is correct. And since coma varies linearly and if you keep the AFOV the same over a range of magnifications, then the coma will appear roughly the same at all of the different magnifications. But it is common for fast Newtonian users to employ a Paracorr with their lowest power eyepieces, but feel they do not need it with shorter focal length eyepieces.

For example, I always use the PC when using my 22NT4 or similar focal length, wide angle eyepiece. But when I switch to higher power, I don't use the PC. For example, I can use 10, 7, 5 and 3.5 XW's, or short fl Nagler T6s without a PC and the field looks sharp except for the very edge, where the image degrades somewhat. This is possible because very high quality short focal length eyepieces are well corrected for off-axis astigmatism at fast f/#s, so in this case all I am seeing is coma, and nothing else. The problem of off-axis astigmatism at fast f/#s is only present at the long focal lengths and ultra wide fields. Off-axis astigmatism scales linearly with eyepiece focal length; a 20mm eyepiece of a given design will have 4 times as much as a 5mm eyepiece of this same design.


Quote:

But, the best-corrected eyepieces of today will have star images tight enough at the edge, if corrected by a coma corrector, to see a globular cluster exit the field with the core still completely resolved. I am certain of that--I've seen M15 exit the edge of my 13 Ethos with the core still resolved into tiny pinpoint star images.
The correction at f/4 won't be as perfect, but the difference will not be that bad. The coma-corrected f/4's star images are still WAY better than the non-coma-corrected f/5's.






The first part sounds perfectly reasonable at f/5. With the PC in place the Ethos eyepiece is working at almost f/6 (f5.75), so its performance should be superb. You did not state what focal length the Ethos is, but the shorter the better. I also see a similar view when using the 10mm or 7mm XW without a PC; I let a bright globular drift across the field and it stays resolved to the core up until the last 5 degrees of apparent field.

My point in all this is that a specific group of eyepieces - 20mm and longer focal length with AFOVs of 70 degrees or more - exhibit off-axis astigmatism with sub f/4 primary mirrors. And I am not talking about war surplus Erfles, I am talking about the best eyepieces money can buy in this group. Extrapolating the performance of these long focal length ultra-wide angle eyepieces at f/5 to what happens at f/3.65 and faster (f/3.3 scopes are in production now) is simply not valid.

And I am not trying to be critical of the eyepieces that are available; the Nagler, Ethos and Pentax XW eyepieces are fantastic and better than anything that has been available to the amateur in the past for low power wide angle view through fast Newtonians. My comments are intended to be informational and to assist others that may own or intend to purchase one of these ultra-fast Newts.

Clear skies,

Ron


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Re: List of Paracorr settings for all brands of EP new [Re: rprice]
      #4661974 - 06/27/11 07:41 PM

Ron,
Al Nagler himself has stated that all their eyepieces are tested at f/4 to have no extra aberrations added due to the fat light cone with its oblique angles. The only design he admitted they have produced that did have astigmatism at the edge of the field were the original Widefields.
He told me that the Panoptic line was developed after the introduction of the Paracorr where, when coma was corrected, the residual astigmatism became visible in the Widefields. After that, their design goal was zero astigmatism.
[and zero angular magnification distortion, but that's another story].

The comatic blur is shaped more like a narrow V that has a faint extension beyond the V shape. It is not astigmatism because it does not change from radial to circumferential on the other side of focus. I suspect many people do not view in skies dark enough to reveal the full extent of the comatic star image. 10X as long as wide might be a slight exaggeration, but it is not unusual for the star image to be many times as wide as the Airy Disc if coma is present.
Coma does not end with the edge of the visible image--it extends to fainter than the eye can see. The camera can capture it, though. Here is a good example of what I see without a coma corrector:
http://www.astronomytelescope.net/images/astronomytelescope99.jpg Would you not describe that as 10X as long as wide when the star image is at the point?
I would.

As for why newtonian users do not employ coma correction at higher powers, I am mystified. I see the exact same coma with my 8mm Ethos barlowed as with my 21 Ethos by itself. I have not see a high enough magnification that the coma was not present. Which is why I use a coma corrector at all magnifications and with all eyepieces. I see it in f/6 scopes, too. It's a matter of expectations: I want center-of-field images at the very edge. I don't get that, but it's close at f/5 with a coma corrector.

I am very familiar with aberrations in eyepieces, and I've owned over 300 of them. I know exactly what astigmatism looks like. One of the ironies of eyepiece design is that leaving positive angular magnification in the eyepiece and solving for rectilinear distortion, as is done on many eyepieces designed for terrestrial use, results in a smaller apparent size for the comatic blur at the edge of the field. That's the case for the Pentax XWs, which have less RD, but as a result, more AMD. Excessive AMD (on a wider design) is probably one of the reasons Pentax did not go wider than the 70 degree field (that, and the fact their spotting scopes don't illuminate a field much wider than that).

One thing I have experienced is that a lot of longer focal length eyepieces have more field curvature than shorter focal lengths (the Pentax XWs are an exception--it is the 20mm and 14mm that have the most field curvature). This tends to bloat the star images at the edge of the field, and exaggerate both coma and astigmatism. The worst "coma" I've seen in a scope was an f/4.3 newtonian without coma correction, using such an eyepiece. The scene in Star Wars when they go to superluminal speeds and you are looking at the stars from the bridge of the Millenium Falcon is only a *slight* exaggeration of what I saw (and some small scopes have star images that look like that all the time).


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Re: List of Paracorr settings for all brands of EP new [Re: bgavin]
      #4662439 - 06/28/11 01:32 AM

Hi Don,

Your conversation with Al Nagler is interesting, but I am not able to dismiss the studies and evaluations that Rutten and Van Venrooij did in their book, and there are others that are more recent. And more importantly, the notion that Nagler and Ethos eyepieces are "perfectly" corrected for f/4 and faster cones is difficult to believe when I see something different in the eyepiece. It would be wonderful if Televue would provide performance graphs or spot diagrams for the long focal length Naglers and Ethos eyepieces showing how they performed at incremental f/ratios from f/5 to f/3. I commend them for providing the performance graphs for the PC1 and PC2.

Regarding your description and picture of coma, that is all quite reasonable. However, what I see at the edge of the field in my 24" f/3.65 with the 22NT4 and PC2 is not coma. It is a blur that goes from radial to circumferential in appearance and is predominantly astigmatism. Without the PC2, I see basically the same thing, only more severe.

As others have pointed out in some of the "fast scope" discussion threads, many have jumped onto the sub f/4 Newtonian bandwagon before all of the details and nuances of these scopes have been proven out, myself included. I am convinced, though, after using my new scope over a hundred times this past year that it is a resounding success and will give me a lifetime of viewing pleasure. But I am also convinced that the unique issues of eyepiece performance in f/3.65 and faster scopes is still being 'shaken out', especially the lowest power, ultra wide field eyepieces.

The fact of the matter is probably that neither the PC2/Nagler or PC2/Ethos combination performs "perfectly" with the sub f/4 Newtonians, but I believe these two are the best choices you have right now at any price. I, too, want center-of-field images at the edge. So, one has to decide if it is worth spending $1000 to $1300 for a low power wide field combo that gives you significantly improved but not "perfect" performance, or wait until something better comes along.

Thanks for your comments.

Clear skies,

Ron


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Re: List of Paracorr settings for all brands of EP new [Re: rprice]
      #5062881 - 02/08/12 08:08 PM


This being a super long thread ..

I would just like to ask if anyone has finally compiled a table showing the Paracorr setting(s) for different eyepieces.


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Re: List of Paracorr settings for all brands of EP new [Re: photiost]
      #5087418 - 02/23/12 02:37 PM

I am slowing determining the settings for my eyepieces. A few days ago I found that the setting for an ES 82 deg 30mm eyepiece is about 2.25. This was in my Paracorr I. I was using a 10" f/4.7 Dob. I primed the Paracorr and focuser with my ES 100 deg 9mm at setting 2.

A setting of 2.25 for the ES 82 30mm produced sharp stars across the FOV. The Double Cluster looked especially nice. I recall seeing a little grouping of reddish stars within the following cluster. Very sharp, good color rendition.

Mike


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Re: List of Paracorr settings for all brands of EP new [Re: photiost]
      #5213464 - 05/09/12 10:20 AM

Quote:


This being a super long thread ..

I would just like to ask if anyone has finally compiled a table showing the Paracorr setting(s) for different eyepieces.





Here is a working list, perhaps someone could review on its accuracy. Kindly add or edit where necessary.

Paracorr setting 1
Meade QX 36mm
Meade Series 4000 UWA 14mm
Pentax XW 14mm, 20mm
Speers-Waler variable 5-8mm
Siebert Observatory Series 34mm
Televue Ethos 10mm, 13mm in 2" mode
Televue Nagler T5 20mm, 31mm
Televue Nagler T2 20mm
Televue Nagler 13mm (original) in 2 mode
Televue Panoptic 41mm, 35mm, 27mm,
Televue Panoptic 22mm in 2 mode
Televue Widefield 32mm

Paracorr setting 2
Explore Scientific 100 9 mm, 14 mm
Meade 5K 34mm SWA
University Optics 40mm MK-70

Paracorr setting 3
1rpd 30mm
Pentax XL 40mm
WO UWAN 28mm
Televue Nagler T4 17mm
Televue Nagler T5 26mm

Paracorr setting 4
Televue Ethos 3.7mm, 6mm, 8mm in 1.25" mode
Televue Nagler 1.25 originals, T5s, T6s all in this series
Televue Radians all in this series
Televue Panoptic 15mm, 19mm, 24mm
Televue Zooms all in this series
Televue Plossls 8-32mm

Paracorr setting 5
Explore Scientific 100 20mm
Explore Scientific 82 4.7mm, 14mm
Meade Series 4000 UWA 8.8mm in 2 mode
Televue Ethos 17mm, 21mm
Televue Ethos 10mm, 13mm in 1.25" mode with TV Hi-Hat 2-1.25 Adaptor
Televue Nagler T5 31mm
Televue Nagler T4 22mm
Televue Nagler T4 12mm in 1.25" mode
Televue Nagler T2 12mm, 16mm in 1.25" mode
Televue Nagler 9mm (original) in 1.25" mode

----------------

Paracorr Type 2

Paracorr setting A
Pentax XW all in this series
Televue Ethos 17mm, 21mm
Televue Nagler T5 31mm
Zeiss Abbe Orthos all in this series

Paracorr setting B
TV Ethos 6mm, 8mm in 1.25" mode
Televue Nagler T4 22mm

Paracorr setting C
Explore Scientific 100 20mm

Paracorr setting D
Televue Ethos 3.7mm in 1.25 mode
Televue Nagler T6s all in this series
Televue Nagler T4 12mm
Televue Nagler T5 16mm
Televue Radians all in this series
Televue Panoptic 19 & 24mm
Televue Nagler Zoom 2-4mm, 3-6mm
Televue Plossls 8-32mm

Paracorr setting E
na

Paracorr setting F
Televue Nagler T4 17mm
Televue Nagler T5 26mm

Paracorr setting G
Televue Nagler T5 20mm
Televue Panoptic 35mm

Paracorr setting H
Televue Ethos 3.7mm, 6mm, 8mm in 2 mode
Televue Panoptic 41mm, 27mm
Televue Plossl 40mm


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Re: List of Paracorr settings for all brands of EP new [Re: Richard Low]
      #5328241 - 07/21/12 12:52 PM

Does anyone know the best setting for a tv 55mm plossl ( smoothside) for the Paracorr type2 ?

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Re: List of Paracorr settings for all brands of EP new [Re: nevy]
      #5334547 - 07/25/12 11:30 AM

Quote:

Does anyone know the best setting for a tv 55mm plossl ( smoothside) for the Paracorr type2 ?



No need to answer this question, I tried it last night at f5 and it doesn't need one , it's pretty sharp at the edges ,( at F10 it's superb) ;-/

Edited by nevy (07/25/12 11:35 AM)


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Re: List of Paracorr settings for all brands of EP new [Re: nevy]
      #5334641 - 07/25/12 12:07 PM

Since that eyepiece produces an 11mm exit pupil in your dob, do you notice the shadow of the secondary? Generally people who have f/5 dobs rarely go longer than about a 31-35mm eyepiece focal length.

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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #5334722 - 07/25/12 12:47 PM

Quote:

Since that eyepiece produces an 11mm exit pupil in your dob, do you notice the shadow of the secondary? Generally people who have f/5 dobs rarely go longer than about a 31-35mm eyepiece focal length.



No I didn't , I didn't expect too much from it in the dob as I bought it mainly for the C11 but I was quite surprised at how good it performed in the dob , I like it alot. The only problem I had was that I needed to pull the eyepiece right to the top of the focuser to achieve focus ,so for safety I will put the tv barrel extender on it next time.


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Re: List of Paracorr settings for all brands of EP new [Re: nevy]
      #5369644 - 08/15/12 07:57 AM

Last Sunday night I took my family to a dark site for the Perseids. To save room in our vehicle, I brought along my 5" f/5 Dob instead of the 10".

While I was there, I tried my Baader Hyperion Zoom in the Paracorr Type I to determine the best setting. I had attempted the Zoom in 1.25" mode before, but of course there was not enough in focus.

I thought I had attempted 2" mode with my 10" Dob and it had not worked (not enough in focus). But this time I made sure to prime the 5" with a TV Plossl 25mm in the Paracorr, and to change the Zoom to 2" mode.

I discovered that the Baader Zoom would indeed come to focus in 2" mode at setting 1. The stars were nice little points of light from center to edge. They were still in focus - or very nearly so - whether the Zoom was at 24mm or 8mm or anywhere in between. Only a very small tweak of the focuser was needed, if at all, at 8mm vs 24mm.

The next time I take my 10" Dob to the dark site I'll retest the Zoom in 2" mode in my Paracorr, being sure to prime it first with the TV Plossl. I'm pleased that the Baader Zoom works well in the Paracorr, since that is the eyepiece that sees the most sky time in my Dobs.

Mike


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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #5369670 - 08/15/12 08:22 AM

Recent updates for eyepiece settings in Paracorr Type 1 - the good, the bad and the ugly!

Baader BGO 9mm: not enough in focus
Sky Watcher Super Plossl 9mm: not enough in focus
Edmund RKE 12mm: Setting 4.75
Baader BGO 12.5mm: not enough in focus
Brandon 16mm: Setting 4
Baader BGO 18mm: not enough in focus
Surplus Shed WF Kellner 19.9mm: Setting 2.5 (for what it's worth )
LOMO Ortho 20mm (12.5x microscope EP): Setting 4.5
Russel RK 20mm: not enough in focus
Faworski Super Abbe Ortho 24mm: Setting 3.75
Sterling Plossl 25.1mm: not enough in focus
Baader Mark-II Zoom (2" mode only): Setting 1 (for all focal lengths)
ES 82deg 30mm: Setting 1.5
Orion Ultrascopic 35mm: not enough in focus
Vixen Ortho 40mm: Setting 3.5

Mike


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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #5369914 - 08/15/12 11:14 AM

Mike,
Since most of these are 1.25" eyepieces, what you need for the ones that require more infocus is an adapter that allows the eyepiece to move substantially closer to the Paracorr's lens.
Here is what you need:
http://www.astrosystems.biz/eyepieceadapter.htm
For a lot of eyepieces, it's worth its weight in gold.


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #5380695 - 08/22/12 09:20 AM

Yes, thanks, Don. I already purchased one of those awhile back. In fact, I think it may have been you that gave me the advice at that time!

The only downside to the adapter is that you need to use a little hex key to secure or remove the eyepiece. I guess I could buy multiple adapters for all my 1.25" eyepieces that won't come to focus any other way in the Paracorr. But that would cost some serious money for me.


Mike


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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #5380703 - 08/22/12 09:26 AM

Update on the Baader Hyperion Zoom: It will also work in my 10" f/4.8 Dob with Paracorr Type 1 Setting 1, as it did in my 5" f/5 Dob. (I primed the Paracorr with my TV Plossl 25mm.) That is what I expected. The particular Newt that the Paracorr is in should not matter.

However, the Baader Zoom must be in 2" mode in order to come to focus.

Mike


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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #5380822 - 08/22/12 10:37 AM

Quote:

Yes, thanks, Don. I already purchased one of those awhile back. In fact, I think it may have been you that gave me the advice at that time!

The only downside to the adapter is that you need to use a little hex key to secure or remove the eyepiece. I guess I could buy multiple adapters for all my 1.25" eyepieces that won't come to focus any other way in the Paracorr. But that would cost some serious money for me.


Mike



Adjust the small setscrew in the adapter so the fit of the eyepiece is tight enough you have to "rotate it in" and "rotate it out". Then, every 1.25" eyepiece can be placed in and removed from the adapter without having to snug down the setscrew on each one.


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #5380887 - 08/22/12 11:09 AM

Thanks, I'll try that.

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Busguy
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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #5381069 - 08/22/12 01:12 PM

Anyone input the Delos line into the settings?

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Starman1
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Re: List of Paracorr settings for all brands of EP new [Re: Busguy]
      #5381374 - 08/22/12 04:31 PM

Quote:

Anyone input the Delos line into the settings?



All the Delos eyepieces except the 17.3 and 14 will use setting "D" with the Paracorr's supplied 1.25" adapter.
The 17.3 and 14 will require setting "A" for right now, also using the 1.25" adapter.
There may be another, lower-profile, 1.25" adapter for the 17.3 and 14.0 a little later on, as the "perfect" correction for those two will require a setting a little farther in than setting "A".
But "A" will still correct a lot better than no Paracorr, in the same way that the original Paracorr didn't completely correct the 31 Nagler or 21 Ethos but they still were improved a lot over no Paracorr.


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miguel gonzalez
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #5423266 - 09/16/12 04:31 AM

Hi all..

I have TV paracorr type 1.

And I have Docter/Zeiss 12.5mm UWA and Nikon Nav Sw 10 mm eyepieces.
What settings should I use in the Paracorr?

Thanks

Edited by miguel gonzalez (09/16/12 12:03 PM)


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Re: List of Paracorr settings for all brands of EP new [Re: miguel gonzalez]
      #5423862 - 09/16/12 02:28 PM

Let's review how to set the Paracorr when you don't know the correct setting and you have no TeleVue eyepieces (if you have a TeleVue eyepiece, use their prescribed setting for that eyepiece and all the other eyepieces will follow--instructions follow:)

Start with the out-most setting of the Paracorr. Focus the telescope and examine the edge of field stars. Still see coma? Move the Paracorr in one setting and refocus. Still see coma, but it's improved? Continue in one more setting.
With trial and error, you will find one setting that produces the least coma at the edge of the field. If aberrations are not fully corrected, it's likely the eyepiece has some residual astigmatism at the edge of the field that the Paracorr won't correct.

Once you have the proper setting for that eyepiece, write it down so you can return the Paracorr to that setting before using that eyepiece the next time.

Now, how to set the other eyepieces once you have a perfect setting for that one eyepiece:
Put the second eyepiece in and focus using the tunable top of the Paracorr. When that eyepiece is in focus, look at the tunable top setting. That will be the setting for that eyepiece. Write it down so you can go to that setting before the next use of that eyepiece.

In that manner, you can do an entire collection of eyepieces without knowing in advance what the settings for those eyepieces are.

As you can see, the tunable top makes all your eyepieces parfocal--only the movement in and out of the tunable top before you insert the next eyepiece is required, plus, perhaps, a tiny bit of refocusing. But the movement of the focuser will be tiny as long as the Paracorr is used.

What if you cannot correct the coma of an eyepiece because the Paracorr's settings don't extend far enough to fully correct that eyepiece?
Well, that's not unusual. The 31 Nagler and 21 Ethos were in that category on the original Paracorr. And the 17.3 and 14 Delos are in that category on the Paracorr II.
Don't worry about it. If the eyepiece is close to the ideal coma correction setting the images will still be improved significantly over no Paracorr at all.
BUT, don't use that eyepiece to determine the settings for your collection. Use an eyepiece that has its best coma correction among the settings of the Paracorr. And, to make sure you have a good starting point, use your eyepiece that has the widest apparent field of view because coma will be more visible in that eyepiece than in narrower field eyepieces.

After you have determined the correct settings for all your eyepieces, even those whose correction is not ideal at one extreme or the other of the Paracorr settings, hopefully you will have written down the settings. If, like me, you don't want to resort to a list before inserting the eyepiece, use a label maker to put the Paracorr setting on the side of the eyepiece so you don't have to remember.

There is an alternative to this, and I admit to using it when I'm using an eyepiece briefly and then inserting another eyepiece: Having the setting absolutely perfect for one eyepiece, I insert another and simply focus using the tunable top. Then, I touch up the focus a tad with the main focuser. That way, I don't even have to read the label on the eyepiece to find the correct setting for the next eyepiece. It helps if you have eyepieces that all use extreme settings (most of mine use one extreme or the other) and your less-often-used eyepieces use an intermediate setting.

So, as you can see, the purpose for this thread is a little unnecessary. All you need to do is take the time to get one eyepiece dialed in and all the rest follow.

Edited by Starman1 (09/16/12 02:31 PM)


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miguel gonzalez
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #5423942 - 09/16/12 03:24 PM

Thank you very much, Don.

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Re: List of Paracorr settings for all brands of EP new [Re: miguel gonzalez]
      #5425364 - 09/17/12 12:42 PM Attachment (88 downloads)

Hello,
I'm using a combination of a universal paracorr (plu-1106) and a tunable top (see attachment). Should I follow the same settings as with type-1 visual?

Another question - can I simply make the distance between eyepiece field lens and the paracorr lens equal to 55mm, or there are other considerations?

thanks in advance.


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Re: List of Paracorr settings for all brands of EP new [Re: Michael11]
      #5425584 - 09/17/12 02:38 PM

Quote:

Hello,
I'm using a combination of a universal paracorr (plu-1106) and a tunable top (see attachment). Should I follow the same settings as with type-1 visual?

Another question - can I simply make the distance between eyepiece field lens and the paracorr lens equal to 55mm, or there are other considerations?

thanks in advance.



When the tunable top is added, you essentially have a Paracorr I, so settings will be the same.
The 55mm spacing is between the lens of the Paracorr and the Focal Plane of the eyepiece. That focal plane can be anywhere in the barrel:
in simple eyepieces it's where the iris (knife-edge baffle) is below the bottom lens of the eyepiece. In complex eyepiece designs it can be in-between lenses.

But, as I mentioned, you only have to get one eyepiece right and you can determine the setting for all the others visually and without measurements.


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Michael11
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #5427437 - 09/18/12 01:35 PM

Ok, thanks.

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Re: List of Paracorr settings for all brands of EP new [Re: Michael11]
      #5465269 - 10/11/12 12:05 PM

Looking at the Televue site, the 13mmT1 (nor any other T1s) are listed. Any ideas why not?

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Re: List of Paracorr settings for all brands of EP new [Re: csrlice12]
      #5465356 - 10/11/12 01:08 PM

Quote:

Looking at the Televue site, the 13mmT1 (nor any other T1s) are listed. Any ideas why not?



Maybe because they haven't been made since the '80s--since before there was a Paracorr?
It would be easy enough to determine the correct setting, though, using the same technique one uses on a non-TeleVue eyepiece (see previous posts).


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #5516696 - 11/12/12 08:36 PM

While I was at my dark site this past weekend waiting for the sky to clear, I determined Paracorr Type I settings for a few more eyepieces:

Astro-Tech Titan-II 40mm: Setting 5
Edmund RKE 28.7: Setting 3
Edmund Plossl 28: Setting 3.5
Brandon 12: Setting 4

Mike


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #5518782 - 11/13/12 10:02 PM

So may I ask this. I have an orion 12" intelliscope and I have een reading here and there about the paracorr. What is a paracorr? I heard it is not 'needed' but it's good to have for fast scopes. What does it do exactly? Do I need it? It seems very expensive but if I do need it...... I will find a way. If I can't ask it in this thread please delete it and I will make a new one. Thanks!!

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Re: List of Paracorr settings for all brands of EP new [Re: Metalmanstan]
      #5518994 - 11/14/12 01:48 AM

A Paracorr is a coma corrector made by TeleVue to correct the coma that is a natural by-product of paraboloidal mirrors. Hence, "Para" "Corr".
What is coma?
It is a stretching out of star images along radial lines (from the center out). In the center, there is no stretching, but the farther from center you go, the more stretched the star images.
The stars at the edge begin to resemble comets. Comets is a word from coma in Latin, which means hair. The constellation Coma Berenices means Bernice's hair.
So coma is an aberration that is present in all newtonian images, but which grows worse quickly the shorter the f/ratio of the scope.
No one thinks they need a coma corrector at f/6. By f/5 it's a generous percentage. By f/4.5 at least 50% feel the need, and by f/4 nearly everyone uses a coma corrector.
Your scope is f/5, so it's nice, but not absolutely essential unless you want the star images at the edge of the field to be just as small and sharp as they are in the center. Most people don't expect that, but once you have some experience with a scope where the stars literally are tiny pinpoints from edge to edge in the field, it's kind of hard to go back to having stars in the outer parts of the field look a little flared.

As a matter of exaggeration, the stars in a fast scope look a little like the stars from the flight deck of the Millenium Falcon jumping to lightspeed (in Star Wars) without coma correction, and look like the same field before the jump to lightspeed with coma correction. Of course, it's not that bad, but you get the idea.

Here's a good article to read on the subject:
http://www.astromart.com/articles/article.asp?article_id=50


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #5519524 - 11/14/12 01:13 PM

In short, a Paracorr sharpens up the view in f5 or shorter reflectors. I resisted for years, but finally got one (used) this year. I'm really pleased with the results, even at f5.

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Re: List of Paracorr settings for all brands of EP new [Re: SteveG]
      #5520244 - 11/14/12 10:19 PM

Does it make it easier to focus the image at high powers or just at any time? and do you need certain eyepieces for it? I had a tough time focusing my 12" f4.9 tonight at about 170x so I was wondering if I needed this? I also started to notice the coma issue tonight. After reading about the paracorr and what it does I started to notice it. I also see that there very expensive.... :-(

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Re: List of Paracorr settings for all brands of EP new [Re: Metalmanstan]
      #5520297 - 11/14/12 10:48 PM

Quote:

Does it make it easier to focus the image at high powers or just at any time? And do you need certain eyepieces for it? I had a tough time focusing my 12" f4.9 tonight at about 170x so I was wondering if I needed this? I also started to notice the coma issue tonight. After reading about the Paracorr and what it does I started to notice it. I also see that they're very expensive.... :-(



No, it doesn't change the on-axis images. If you were having trouble focusing, perhaps the seeing conditions just didn't allow that high a power to be used. I've seen nights where 100X was really pushing it on my 12.5", but other nights where 608X was possible.
It's the luck of the draw, assuming your optics are cooled down and your scope is collimated. If it looked good at lower powers, it was probably seeing.

You don't need special eyepieces for a coma corrector.

Yes, they are expensive, but they are on sale right now, so they are a little less expensive. Many people balk at the high price. It's quite understandable.


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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #5520785 - 11/15/12 09:15 AM

With an f/4.9, I would just look for a used Type 1 Paracorr rather than spending the princely sum being asked for the Type 2. They can typically be found on the used market for $175-$225.

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Re: List of Paracorr settings for all brands of EP new [Re: Doug Culbertson]
      #5520853 - 11/15/12 09:57 AM

Quote:

With an f/4.9, I would just look for a used Type 1 Paracorr rather than spending the princely sum being asked for the Type 2. They can typically be found on the used market for $175-$225.




That's what I did. In my world, the full price of a new Paracorr Type 2 is out of the question. At f/4.8, my optics don't need correction that badly.

Mike


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Re: List of Paracorr settings for all brands of EP new [Re: Sarkikos]
      #5521188 - 11/15/12 12:58 PM

Quote:

Quote:

With an f/4.9, I would just look for a used Type 1 Paracorr rather than spending the princely sum being asked for the Type 2. They can typically be found on the used market for $175-$225.




That's what I did. In my world, the full price of a new Paracorr Type 2 is out of the question. At f/4.8, my optics don't need correction that badly.

Mike




As did I - yes the full price is too much! I think I paid $215 for my Type 1, tunable top model. It should be noted that it adds a magnification factor of 1.15x.


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Re: List of Paracorr settings for all brands of EP new [Re: SteveG]
      #5576571 - 12/17/12 10:43 PM

Sarikakis,
You should publish your findings as a list for Paracorr 1 and Paracorr 2. I own the PC 1 w tunable top. I have a 12.5" dob at f/4.0. With the PC it is 4.6. I was surprised to see that you believe the Nagler 22T4 requires a deeper/lower/closer setting than the ES 20mm 100 deg. I find that surprising. Similarly you find the ES 30mm 82 N2 is easily handled in the PC1, but the Nagler 31mm T5 cannot properly in-focus and must "bottom out" for its improved results--not optimal. Same with Ethos 17 and 21mm. Sounds like you are recommending ES series WFOV eyepieces for budget constrained PC1 owners as they fit. Thanks for the analysis.


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Re: List of Paracorr settings for all brands of EP new [Re: ohioalfa64]
      #5625640 - 01/16/13 04:43 AM

So am I right in thinking that Televue is not publishing Delos settings for the Paracorr type I?

gb.


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Re: List of Paracorr settings for all brands of EP new [Re: gb_astro]
      #5626079 - 01/16/13 12:04 PM

Quote:

So am I right in thinking that Televue is not publishing Delos settings for the Paracorr type I?

gb.



The 12mm and shorter use the same setting as other TeleVue 1.25" eyepieces.
The 17.3 and 14 would use the top turned in all the way and that wouldn't be quite far enough for ideal correction, but it will still be a big improvement.

And, as has been mentioned, if you have even one eyepiece for which a perfect setting has been found or dialed in, you can insert any other eyepiece and focus using the tunable top. When you achieve focus, that setting will be ideal for that eyepiece. Next time, you can pre-set the tunable top to that setting before inserting the eyepiece.


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Re: List of Paracorr settings for all brands of EP new [Re: ohioalfa64]
      #5626147 - 01/16/13 12:53 PM

ohioalfa64,

Quote:

Sarikakis,
You should publish your findings as a list for Paracorr 1 and Paracorr 2. I own the PC 1 w tunable top. I have a 12.5" dob at f/4.0. With the PC it is 4.6. I was surprised to see that you believe the Nagler 22T4 requires a deeper/lower/closer setting than the ES 20mm 100 deg. I find that surprising. Similarly you find the ES 30mm 82 N2 is easily handled in the PC1, but the Nagler 31mm T5 cannot properly in-focus and must "bottom out" for its improved results--not optimal. Same with Ethos 17 and 21mm. Sounds like you are recommending ES series WFOV eyepieces for budget constrained PC1 owners as they fit. Thanks for the analysis.




This isn't my thread. I've only contributed some of the eyepiece settings. I don't own any Naglers or Ethos, and I don't have an ES 20mm 100, so I can't say anything about those settings.

However, I do recommend ES eyepieces. All of mine have performed well in my Paracorr Type 1. None of my ES have needed more in-focus or out-focus than the Paracorr 1 could provide.

Mike


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gb_astro
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #5627096 - 01/16/13 09:56 PM

Quote:

Quote:

So am I right in thinking that Televue is not publishing Delos settings for the Paracorr type I?

gb.



The 12mm and shorter use the same setting as other TeleVue 1.25" eyepieces.
The 17.3 and 14 would use the top turned in all the way and that wouldn't be quite far enough for ideal correction, but it will still be a big improvement.

And, as has been mentioned, if you have even one eyepiece for which a perfect setting has been found or dialed in, you can insert any other eyepiece and focus using the tunable top. When you achieve focus, that setting will be ideal for that eyepiece. Next time, you can pre-set the tunable top to that setting before inserting the eyepiece.




Great, thanks,
gb.


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photiost
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Re: List of Paracorr settings for all brands of EP new [Re: gb_astro]
      #5657151 - 02/01/13 09:14 PM

This is a VERY long thread as many people have contributed very useful information on this topic

Just wondering if anyone has been keeping track of the posts and the reported settings for various eyepieces posted here ...
if so, perhaps a table or partial list exists ?

I did find most of the TV eyepieces with their Paracorr settings posted on their website
.


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maire
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Re: List of Paracorr settings for all brands of EP new [Re: photiost]
      #5856891 - 05/13/13 06:51 AM

I can't read all posts... Is there a pdf file for Parracor type 2 settings for other brands?
Eric

Edited by maire (05/13/13 06:57 AM)


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Re: List of Paracorr settings for all brands of EP new [Re: photiost]
      #5883432 - 05/25/13 02:13 AM

Quote:

This is a VERY long thread as many people have contributed very useful information on this topic

Just wondering if anyone has been keeping track of the posts and the reported settings for various eyepieces posted here ...
if so, perhaps a table or partial list exists ?

I did find most of the TV eyepieces with their Paracorr settings posted on their website
.




There is a sign in the break room at my workplace which says, "If you see a mess, you own it".



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Re: List of Paracorr settings for all brands of EP new [Re: Metalmanstan]
      #5947896 - 06/30/13 11:34 AM

Quote:

Does it make it easier to focus the image at high powers or just at any time? and do you need certain eyepieces for it? I had a tough time focusing my 12" f4.9 tonight at about 170x so I was wondering if I needed this? I also started to notice the coma issue tonight. After reading about the paracorr and what it does I started to notice it. I also see that there very expensive.... :-(




Actually, I have found the Paracorr useful on occassion for focussing: Often when I am hunting a planetary nebula, and I have a fuzzy object in the center, being able to focus right out the the edge ensures the blurriness is from the object, not my focus.


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Re: List of Paracorr settings for all brands of EP new [Re: Doc Willie]
      #6112760 - 10/02/13 10:02 AM

I recently upgraded to a Paracorr II. On my last trip to a dark site, I determined a couple settings for the PII.

Leica ASPH: A, and then focus a little in.

LVW 8: A.5 (halfway between A & B)

Mike


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Starman81
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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #6227983 - 12/01/13 09:17 PM

Quote:

Quote:

Anyone input the Delos line into the settings?



All the Delos eyepieces except the 17.3 and 14 will use setting "D" with the Paracorr's supplied 1.25" adapter.
The 17.3 and 14 will require setting "A" for right now, also using the 1.25" adapter.
There may be another, lower-profile, 1.25" adapter for the 17.3 and 14.0 a little later on, as the "perfect" correction for those two will require a setting a little farther in than setting "A".
But "A" will still correct a lot better than no Paracorr, in the same way that the original Paracorr didn't completely correct the 31 Nagler or 21 Ethos but they still were improved a lot over no Paracorr.




Don, will the 17.3/14 Delos only come close to working optimally with the Type 2 ParaCorr? I tried both in my Type 1 (PCV-2000) on setting 1 and the 14 Delos edge performance compared to the XW 14 left much to be desired in the f/4.3 STS 11.


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Re: List of Paracorr settings for all brands of EP new [Re: Starman81]
      #6228238 - 12/02/13 12:26 AM

Quote:

Quote:

Quote:

Anyone input the Delos line into the settings?



All the Delos eyepieces except the 17.3 and 14 will use setting "D" with the Paracorr's supplied 1.25" adapter.
The 17.3 and 14 will require setting "A" for right now, also using the 1.25" adapter.
There may be another, lower-profile, 1.25" adapter for the 17.3 and 14.0 a little later on, as the "perfect" correction for those two will require a setting a little farther in than setting "A".
But "A" will still correct a lot better than no Paracorr, in the same way that the original Paracorr didn't completely correct the 31 Nagler or 21 Ethos but they still were improved a lot over no Paracorr.




Don, will the 17.3/14 Delos only come close to working optimally with the Type 2 ParaCorr? I tried both in my Type 1 (PCV-2000) on setting 1 and the 14 Delos edge performance compared to the XW 14 left much to be desired in the f/4.3 STS 11.




TeleVue now makes an "In Travel" adapter that drops the shoulder of the 17.3 and 14 Delos 1/8" below the top of the Paracorr. If the 17.3 and 14 are used with this adapter, they become parfocal with the 12-3.5mm range when those are used with the standard adapter that comes in the Paracorr.
If there is an optimum setting for the 3.5-12mm Delos in the Paracorr 1 (and they would all use the same setting), the use of the In-Travel adapter will allow the 17.3mm and 14mm to use the same setting as all the other Delos eyepieces.
Since the short focal length Delos are parfocal with most of TeleVue's 1.25" eyepieces, and none of them used setting 1 in the original Paracorr, the key is to use the correct setting for the other 1.25" eyepieces (I can't remember if it was setting 2 or 4 when using the supplied 1.25" adapter) and use that same setting for the Delos range.
If the 17.3mm and 14mm Delos are then used with the new adapter, that setting would also be optimum for them.


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Starman81
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Reged: 03/06/08

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Re: List of Paracorr settings for all brands of EP new [Re: Starman1]
      #6228927 - 12/02/13 11:38 AM

Quote:


TeleVue now makes an "In Travel" adapter that drops the shoulder of the 17.3 and 14 Delos 1/8" below the top of the Paracorr. If the 17.3 and 14 are used with this adapter, they become parfocal with the 12-3.5mm range when those are used with the standard adapter that comes in the Paracorr.
If there is an optimum setting for the 3.5-12mm Delos in the Paracorr 1 (and they would all use the same setting), the use of the In-Travel adapter will allow the 17.3mm and 14mm to use the same setting as all the other Delos eyepieces.
Since the short focal length Delos are parfocal with most of TeleVue's 1.25" eyepieces, and none of them used setting 1 in the original Paracorr, the key is to use the correct setting for the other 1.25" eyepieces (I can't remember if it was setting 2 or 4 when using the supplied 1.25" adapter) and use that same setting for the Delos range.
If the 17.3mm and 14mm Delos are then used with the new adapter, that setting would also be optimum for them.




Thanks Don. The setting for 1.25" TV eyepieces in the ParaCorr Type 1 is setting 4, so I'll have to try them out with the In-Travel adapter.


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Phillip Creed
Idiot Seeking Village
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Reged: 07/25/06

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Re: List of Paracorr settings for all brands of EP new [Re: Starman81]
      #6453518 - 04/07/14 08:34 PM

Paracorr Type-1:

30ES-82: Setting ~ 1.7 (closer to "2" than to "1").

This would put it at around the same setting as a 20T5, if you're thinking about a Baader MPCC for this eyepiece.

Clear Skies,
Phil


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