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Equipment Discussions >> Eyepieces

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Sarkikos
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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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Metalmanstan
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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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Starman1
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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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SteveG
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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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Metalmanstan
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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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Starman1
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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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Doug Culbertson
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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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Sarkikos
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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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SteveG
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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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ohioalfa64
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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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gb_astro
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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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Starman1
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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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Sarkikos
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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
sage


Reged: 01/01/08

Loc: Sydney, Australia
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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Loc: France
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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Starman81
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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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Doc Willie
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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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Sarkikos
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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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