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Equipment Discussions >> Eyepieces

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SkyRanger
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Reged: 10/21/10

Loc: Prescott Valley, AZ
Re: Delos 17.3---VERY Sad new [Re: Richard Low]
      #5166057 - 04/10/12 10:48 PM

NO luck getting the D17 to focus in my 8" dob. There is just no way to get more infocus other than shortening my poles- which I am not willing to do. With only a 1.25 focuser there is no way to play tricks with adaptors. Next time I will check the stats and not assume!

Gordon


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John Rhodes
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Re: Delos 17.3---VERY Sad new [Re: SkyRanger]
      #5166257 - 04/11/12 01:49 AM

Quote:

NO luck getting the D17 to focus in my 8" dob. There is just no way to get more infocus other than shortening my poles- which I am not willing to do. With only a 1.25 focuser there is no way to play tricks with adaptors. Next time I will check the stats and not assume!

Gordon



Gordon,
Try re-collimating the mirror with it as forward toward the focuser as possible that you can get good collimation... this often works.


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Richard Low
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Re: Delos 17.3---VERY Sad new [Re: John Rhodes]
      #5166339 - 04/11/12 05:32 AM

Quote:

Quote:

NO luck getting the D17 to focus in my 8" dob. There is just no way to get more infocus other than shortening my poles- which I am not willing to do. With only a 1.25 focuser there is no way to play tricks with adaptors. Next time I will check the stats and not assume!

Gordon



Gordon,
Try re-collimating the mirror with it as forward toward the focuser as possible that you can get good collimation... this often works.




looks like i really wont be able to try out this eyepiece in my dobs as i may not have enough in-focus and Paracorr issues...sigh...


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SkyRanger
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Re: Delos 17.3---VERY Sad new [Re: Richard Low]
      #5166362 - 04/11/12 06:16 AM

John, Thanks for the tip, but I have tried moving the mirror forward already--just not quite enough slack with the PB8. I am disappointed since I really enjoy the D6 and D10. At least for now, I will stick with the N17 in my scopes with 2" focusers.

Gordon


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sniperpride
super member


Reged: 01/04/12

Re: Delos 17.3---VERY Sad new [Re: SkyRanger]
      #5167554 - 04/11/12 08:39 PM

Gordon, does it work with your 12.5?

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Pingu
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Reged: 11/06/11

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Re: Delos 17.3---VERY Sad new [Re: sniperpride]
      #5167564 - 04/11/12 08:43 PM

Thankfully, I haven't a problem at all with my D17 in my XT8.

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SkyRanger
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Re: Delos 17.3---VERY Sad new [Re: Pingu]
      #5167566 - 04/11/12 08:49 PM

Snipe, my 12.5 is loaned out to a friend. It has a 2" focuser, and I predict the D17 would work in the larger Portaball. I love the Nagler 17 in that scope and at this point I am sticking with the Nagler. The D17 sold quickly on a site we all know of, and I am sending it out with tear drops on its huge eye lens.

Gordon


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jeffdetweiler
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Reged: 09/23/12

Re: Delos 17.3---VERY Sad new [Re: Richard Low]
      #5541108 - 11/26/12 09:38 PM

Astro Systems makes a 2" - 1 1/4" adapter in which a 1 1/4" eyepiece drops about 1/2" down into the adapter to give you an extra 1/2" of in focus

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Sarkikos
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Re: Delos 17.3---VERY Sad new [Re: Jeff Morgan]
      #5541213 - 11/26/12 10:39 PM

Jeff,

Quote:

I seem to have an instinctive need to play with focus whenever I change eyepieces. Since I have a nice focuser, parfocal has never been an issue for me.




I agree. I never got this preoccupation with parfocality - is that a word? - in eyepieces. That factor flies well below my radar. I don't give a fig if my eyepieces are parfocal or not. I just don't get it. What's a focuser for?

On the other hand, it is not a good thing if an eyepiece needs more focus or less focus than my focuser will allow. I'd rather not deal with extensions and low-profile adapters.

Mike


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Deep13
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Reged: 01/25/05

Loc: NE Ohio
Re: Delos 17.3---VERY Sad new [Re: Sarkikos]
      #5541402 - 11/27/12 12:34 AM

If it doesn't come to focus, it is not really an eyepiece. Swing and a miss from TV.

And as far as moving the mirror forward a tiny bit with collimation, 1. what does the scope's manufacturer say about that? 2. why should have screw around with that? Shouldn't the eyepiece work with commercially produced scopes as they are? I can see mickey mousing it with an eyepiece made from spare lenses you got from Surplus Shed or with a DIY scope, but not a "premium" "EP" on a Newt that works with ever other EP.


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ThreeD
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Reged: 12/23/08

Loc: Sacramento suburbs
Re: Delos 17.3---VERY Sad new [Re: Deep13]
      #5541444 - 11/27/12 01:38 AM

Quote:

If it doesn't come to focus, it is not really an eyepiece. Swing and a miss from TV.

And as far as moving the mirror forward a tiny bit with collimation, 1. what does the scope's manufacturer say about that? 2. why should have screw around with that? Shouldn't the eyepiece work with commercially produced scopes as they are? I can see mickey mousing it with an eyepiece made from spare lenses you got from Surplus Shed or with a DIY scope, but not a "premium" "EP" on a Newt that works with ever other EP.


I've read of premium dob buyers cutting trusses to the proper length upon arrival of their scope. Loosening the collimation bolts a turn or two is nothing...

Are you sure the scope works with *every* other EP? Do you own every other EP and have you tried them all? I'm sure there are a few others out there that won't work in that scope too unless the mirror is moved forward -- and the numbers will be even larger if you want to use a barlow or a Paracorr as they both require more in-focus.

I know that to use my 31T5 Nagler with a Paracorr and have it achieve focus in my LB I need to make sure the mirror isn't pulled all the way back. I prefer to have my cell pulled back as it stiffens the cell and ensures it won't shift. However, I do need to run it relaxed just a bit to make that combination work. Luckily it's not enough to make it to where cell shift is a problem. Would you also claim that a Terminagler/Paracorr combination is a swing and a miss??


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Stellarfire
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Reged: 07/10/11

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Re: Delos 17.3---VERY Sad new [Re: Mr. Bill]
      #5541461 - 11/27/12 02:30 AM

Quote:

Just a reminder....TV website ep specs page gives fieldstop location referenced from the ep shoulder for all their current eps.

Use it and there will be no more surprises after ordering TV eps.







Yes. By the way: According that TeleVue spec page, the new 14mm Delos will have the same field stop location like the 17.3mm Delos. All other Delos models are parfocal.

Stephan


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Sarkikos
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Loc: Nyctophobia, Maryland, USA
Re: Delos 17.3---VERY Sad new [Re: Stellarfire]
      #5541582 - 11/27/12 07:16 AM

If there is not enough in-focus for an eyepiece, and you have an old-style tall focuser, you could upgrade to a low-profile. Or if you have a truss scope, you could shorten the trusses. Or you could raise the mirror in a tube scope. But then you might need to buy extensions for your other eyepieces...

Or you could return the eyepiece or sell it to someone else. Cut your losses, don't shorten the scope.


Mike


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Jeff Morgan
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Re: Delos 17.3---VERY Sad new [Re: Deep13]
      #5541760 - 11/27/12 10:01 AM Attachment (22 downloads)

Quote:

If it doesn't come to focus, it is not really an eyepiece. Swing and a miss from TV.

And as far as moving the mirror forward a tiny bit with collimation, 1. what does the scope's manufacturer say about that? 2. why should have screw around with that? Shouldn't the eyepiece work with commercially produced scopes as they are? I can see mickey mousing it with an eyepiece made from spare lenses you got from Surplus Shed or with a DIY scope, but not a "premium" "EP" on a Newt that works with ever other EP.




A relevant topic for me, since I just finished focus testing (trimming truss tubes) on my new project. Daylight focus on a distant hill works, star test is next.

Firstly, trimming tubes is not a big deal. Even if you have no tools a trip to the hardware store for a hacksaw, mitre box, and file will set you back about $25 and do an acceptable job. And if you have a table saw, it is a trivial job. I would prefer this solution over using the collimation screws or moving the mirror cell up the tube (for solid tube scopes).

A swing and a miss on the Delos 17.3 and 14? Hardly! They both appear to require just a bit less in-travel than the 31 Nagler, which is perhaps the most common maximum field sweepers you will find on Dobs today. If you can make the 31N focus, the 17.3/14 Delos should also focus.

As far as focus travel, most of us inflict that pain upon ourselves by selecting focusers with minimum travel distance. I just did it to myself also, buying a 1-1/2" travel focuser instead of the 2" travel I have used in previous builds. I can reach with the 31 Nagler and 14 Delos, and most of the rest of my eyepieces will reach focus within my focuser range, with one exception - the 48 Brandon. It requires an extension tube. Annoying, but not a show stopper. Had I chosen the 2" travel focuser, they would all reach with no extension tube but that is the nature of choices, no?

What would the manufacturer would say about moving the mirror forward? There is a reason those collimation screws are left that long ....


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Sarkikos
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Re: Delos 17.3---VERY Sad new [Re: Jeff Morgan]
      #5541780 - 11/27/12 10:12 AM

Quote:

Firstly, trimming tubes is not a big deal. Even if you have no tools a trip to the hardware store for a hacksaw, mitre box, and file will set you back about $25 and do an acceptable job. And if you have a table saw, it is a trivial job. I would prefer this solution over using the collimation screws or moving the mirror cell up the tube (for solid tube scopes).




Trimming truss tubes should not be a problem. Resizing a solid tube - or moving a mirror up in tubes where the cell attaches directly to the tube end - can be a problem. Well, IS a problem for me with my lack of metal-working skills, metal-working equipment and the space for metal-working.


Mike


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Starman1
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Re: Delos 17.3---VERY Sad new [Re: Sarkikos]
      #5541838 - 11/27/12 10:43 AM

Quote:

Jeff,

Quote:

I seem to have an instinctive need to play with focus whenever I change eyepieces. Since I have a nice focuser, parfocal has never been an issue for me.




I agree. I never got this preoccupation with parfocality - is that a word? - in eyepieces. That factor flies well below my radar. I don't give a fig if my eyepieces are parfocal or not. I just don't get it. What's a focuser for?

On the other hand, it is not a good thing if an eyepiece needs more focus or less focus than my focuser will allow. I'd rather not deal with extensions and low-profile adapters.

Mike



One of the great things about the Paracorr, other than eliminating coma and flattening the field, is that it makes every eyepiece parfocal.
If one presets the Paracorr's tunable top before the next eyepiece is inserted, the amount of focuser travel to get to perfect focus is negligible.
All my eyepieces focus in +/- 1mm.
Or, one can insert the new eyepiece and focus using the tunable top.
Either way, each eyepiece will have its correct setting and the amount of focuser shift from one eyepiece to the next will be negligible.
The only reason it might not have been wise for me to use a focuser with <1/2" travel is that there may be accessories I don't yet have that wouldn't focus in that range. If I used binoviewers, for example, they are typically used without a Paracorr, and the focal position could be well away from where the Paracorr is positioned.

Oh, that and the Delos 17.3 and 14 require a little more in-travel of the Paracorr's tunable top than is allowed in the Paracorr design. There are a couple adapters that could work
to mitigate this.
However, this may not be enough in the Paracorr I. There, some experimentation would be necessary.
But, you'll be closer to parfocal than not using a Paracorr at all.

Edited by Starman1 (11/27/12 10:50 AM)


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dcoyle
professor emeritus


Reged: 10/11/05

Loc: Turbulent but dark skies, N.M.
Re: Delos 17.3---VERY Sad new [Re: Jeff Morgan]
      #5541853 - 11/27/12 10:54 AM

An OT moment, please.

Jeff, That is an amazing scope! What size and f/ is it?

Thanks,

Dan


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Scanning4Comets
Markus
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Reged: 12/26/04

Loc: Ontario, Canada
Re: Delos 17.3---VERY Sad new [Re: Sarkikos]
      #5541862 - 11/27/12 10:57 AM

When I received my new crayford focuser I thought I needed an extension tube to reach focus for all of my eyepieces, but it turns out that the one I got can go outwards about another 1/4" so I was in business. Someone on here mentioned moving my mirror back a bit, so that helped as well.

I can now use ALL of my eyepieces without the extension tube and I was also awarded with another added bonus:

I can use my two extension tubes with filters attached to them, so when I need to use my 2" filters, I just plop the extension tube with Orion Ultrablock or 2" Polarizer, then add the eyepiece into the tube and I can still reach focus!

No more fumbling in the dark screwing filters onto eyepieces !!! I DESPISE doing that because half the time I try that, the threads don't catch or they will try to cross-thread. I have almost dropped the filters so many times when trying to screw them onto the barrels of my adapters.

I will never go back to screwing filters onto barrels ever again!

So, in relation to the original poster here, and others who think it is a bummer if you need to fiddle a bit in order to actually REACH FOCUS, consider yourselves lucky! Sometimes you can't get focus at all. A few twists of the collimation screws, or truss adjustments is half the fun in achieving focus sometimes!



Cheers,


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Sarkikos
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Re: Delos 17.3---VERY Sad new [Re: Starman1]
      #5541869 - 11/27/12 11:06 AM

Don,

Quote:

One of the great things about the Paracorr, other than eliminating coma and flattening the field, is that it makes every eyepiece parfocal.
If one presets the Paracorr's tunable top before the next eyepiece is inserted, the amount of focuser travel to get to perfect focus is negligible.
All my eyepieces focus in +/- 1mm.
Or, one can insert the new eyepiece and focus using the tunable top.
Either way, each eyepiece will have its correct setting and the amount of focuser shift from one eyepiece to the next will be negligible.




I have not done this yet but it sounds like a worthy experiment for next New Moon at my dark site. So far, I haven't kept the Paracorr in the focuser consistently, but only use it now and then for specific eyepieces.

One problem that I've found when setting my Paracorr I for different eyepieces, is that the tuning knob sticks. Often I need to loosen both the tuning knob and the set screw that detains the 1.25" adapter in order to turn the tuning top. This is a PITA at a dark site.

Mike


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Sarkikos
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Re: Delos 17.3---VERY Sad new [Re: Scanning4Comets]
      #5541915 - 11/27/12 11:33 AM

Mark,

Quote:

I can use my two extension tubes with filters attached to them, so when I need to use my 2" filters, I just plop the extension tube with Orion Ultrablock or 2" Polarizer, then add the eyepiece into the tube and I can still reach focus!

No more fumbling in the dark screwing filters onto eyepieces !!! I DESPISE doing that because half the time I try that, the threads don't catch or they will try to cross-thread. I have almost dropped the filters so many times when trying to screw them onto the barrels of my adapters.

I will never go back to screwing filters onto barrels ever again!




Yep, I use that trick for 2" filters, too. It also allows you to keep the same filter on the scope and change eyepieces. A friend had a 2" filter wheel I thought about buying, but I thought again and decided not to. In a Dob, you'd probably need an OCA to come to focus, thereby halving the effective focal length of the eyepiece. That would ruin the whole idea of using low power eyepieces with a 2" filter. (The extra weight would also be a bear to deal with.)

But for medium-to-high power, a wheel for 1.25" filters is great. I have a wheel permanently loaded with DSO filters for trips to the dark site. Nothing like viewing M42 with a Baader Zoom on a filter wheel. You can immediately vary the image scale and the DSO filter as you wish.

That's one of the main reasons I don't have a Paracorr permanently installed in my focuser!


Mike


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