Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Mid-20's mm 1-1/4 Eyepiece for C8 SCT with ~20mm eye relief and max field stop

Eyepieces SCT
  • Please log in to reply
30 replies to this topic

#1 GGK

GGK

    Vostok 1

  • *****
  • topic starter
  • Posts: 155
  • Joined: 04 Jan 2021
  • Loc: SouthWest Florida

Posted 22 April 2021 - 02:27 PM

Looking for eyepiece options for my C8 that will maximize TFOV in a 1-1/4 eyepiece format.

 

1-1/4 format

About 20mm eye relief. Longer is OK, but can't be much shorter.

Maximum field stop

Ballpark of 70 degrees APOV is most comfortable

Probably in the 24 - 28mm range

 

If they made them in this focal length, I would buy a Delos or Pentax XW.

 

I've found the ES68 24mm, but eye relief is on the short side, so I was looking for other options that will work OK at F10 and also with a f6.3 focal reducer.

 

Again - 1-1/4 only because I want to use it in a 1-1/4 micro-focusing eyepiece clamp on a T2 prism diagonal.  I'm all set on 2-inch equipment.

 

I appreciate all suggestions because I really can't find much that fits the description.

 

Thanks,

 

Gary

 



#2 jmillsbss

jmillsbss

    Viking 1

  • *****
  • Posts: 673
  • Joined: 03 Dec 2018
  • Loc: New Albany, Mississippi, USA

Posted 22 April 2021 - 02:34 PM

https://www.eyepiece..._p/17102024.htm

 

Granted, he's out of stock, but they're pretty good from what I hear.


  • havasman, Jimceez and GGK like this

#3 Jeffmar

Jeffmar

    Apollo

  • -----
  • Posts: 1,330
  • Joined: 18 Mar 2012
  • Loc: salt lake city, utah

Posted 22 April 2021 - 03:05 PM

I like my Pentax eyepieces. I have 10mm, 14mm, and 20mm eyepieces in that brand. They have a 20mm eye relief and a 70 degree apparent field. 


  • rmille61611 and GGK like this

#4 photoracer18

photoracer18

    Skylab

  • *****
  • Posts: 4,094
  • Joined: 02 Sep 2013
  • Loc: Martinsburg, WV

Posted 22 April 2021 - 03:13 PM

The problem in the 24-28mm range is that the 1.25" barrel is the field stop. At 28mm the most field you can get is about 55 degrees. Its the reason why Pentax stopped making the XL 28 in 1.25"  (55 degrees) and went to the 30mm 2" in the XW 30 (70 degrees). 24mm is a little better but the limit due to the barrel is about 60 degrees in 1.25". No free lunch when optical physics is involved. And getting 20mm of eye relief constricts in more.


Edited by photoracer18, 22 April 2021 - 03:15 PM.

  • Dave Mitsky and GGK like this

#5 Virtus

Virtus

    Mariner 2

  • *****
  • Posts: 233
  • Joined: 09 Mar 2021
  • Loc: SE NC

Posted 22 April 2021 - 03:22 PM

https://www.eyepiece..._p/17102024.htm

 

Granted, he's out of stock, but they're pretty good from what I hear.

Yeah, I bought the last one from Don lol.gif but would recommend the APM if you can find it anywhere else.

 

I'm using it in a C6 with the same diagonal setup; haven't used it with a reducer yet but am planning to tonight.


  • GGK likes this

#6 cst4

cst4

    Viking 1

  • *****
  • Posts: 704
  • Joined: 06 Jun 2018

Posted 22 April 2021 - 03:28 PM

Vixen 22mm LVW

APM 24mm UFF (or one of the other brands with same optics)

Celestron 25mm XCel LX

Pentax 20mm XW

Baader 22mm and 24mm Hyperions

ES 26mm 62 degree

 

All of the above have long eye relief.  There are other discontinued options on the used market, but these above are all still out there new.  I listed them in order of my favorite to least favorite.  The 25mm XCel LX is the best bang for buck and is also smaller and lighter than most of the other options.  The ES 26mm is small and fairly decent price as well but it's not quite the same quality as the others in my opinion.


Edited by cst4, 22 April 2021 - 03:31 PM.

  • Dave Mitsky, rmille61611 and GGK like this

#7 wrvond

wrvond

    Mercury-Atlas

  • *****
  • Posts: 2,844
  • Joined: 25 Sep 2014
  • Loc: West Virginia

Posted 22 April 2021 - 03:35 PM

Here are all the 1.25" EP's I use. Not all are suitable for what you are using, but this is just part of a much larger workbook.

These are, of course, TVs, but it should be close for other brands as well, I would think.

Two tables, one without reducer and one with.

Hope it helps.

 

1.25 inch.JPG


Edited by wrvond, 22 April 2021 - 03:36 PM.

  • GGK likes this

#8 Virtus

Virtus

    Mariner 2

  • *****
  • Posts: 233
  • Joined: 09 Mar 2021
  • Loc: SE NC

Posted 22 April 2021 - 03:40 PM

Vixen 22mm LVW

APM 24mm UFF (or one of the other brands with same optics)

Celestron 25mm XCel LX

Pentax 20mm XW

Baader 22mm and 24mm Hyperions

ES 26mm 62 degree

 

All of the above have long eye relief.  There are other discontinued options on the used market, but these above are all still out there new.  I listed them in order of my favorite to least favorite.  The 25mm XCel LX is the best bang for buck and is also smaller and lighter than most of the other options.  The ES 26mm is small and fairly decent price as well but it's not quite the same quality as the others in my opinion.

I thought the Vixens were discontinued?


  • GGK likes this

#9 cst4

cst4

    Viking 1

  • *****
  • Posts: 704
  • Joined: 06 Jun 2018

Posted 22 April 2021 - 04:03 PM

Virtus,

You may be correct.  I do not see the 22 LVW in stock on any websites.  My mistake.

It's a shame though, that is a great eyepiece.  I did think though that the 24mm UFF provided nearly identical views in my Access and C6.  


  • GGK likes this

#10 Starman1

Starman1

    Vendor (EyepiecesEtc.com)

  • *****
  • Vendors
  • Posts: 50,280
  • Joined: 23 Jun 2003
  • Loc: Los Angeles

Posted 22 April 2021 - 04:22 PM

We continue to see recommendations for the 22mm Vixen LVW almost a decade after it was discontinued as if there were still thousands of them out there.

I have some recommendations:

24mm Baader Hyperion--not bad at f/10 but not good at f/5.  It has a 28.5mm field stop--the widest in a 1.25".  Long eye relief, 68° field.

24mm APM Ultra Flat Field--better optically and only a tad smaller true field.  Also available as a Meade UHD, an Altair Ultra Flat, a Celestron Ultima Edge and an Orion UltraFlat. Long eye relief, 65° field.

20mm Pentax XW--excellent long eye relief 70° eyepiece, but with a smaller true field than the others.

 

As the focal length exceeds 24mm, the apparent field narrows.

To wit: 26mm (62°), 32mm Plössl (49.5°), 40mm Plössl (40°).  Both have the maximum field for 1.25", but a narrower apparent field.


Edited by Starman1, 22 April 2021 - 04:23 PM.

  • Dave Mitsky, rmille61611, GeneT and 1 other like this

#11 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • Posts: 5,396
  • Joined: 31 Aug 2009

Posted 22 April 2021 - 04:44 PM

Again - 1-1/4 only because I want to use it in a 1-1/4 micro-focusing eyepiece clamp on a T2 prism diagonal.  I'm all set on 2-inch equipment.

I guess I don't understand this argument. Generally, being "all set on" means you already have or are wanting to go to 2" EPs/equipment.

 

And especially in the mid-20mm range all of the wide field options are already 2". And here there are a couple of real standouts:: 25ES100 and the venerable 31NT5, both playing the part of hand grenades when necessary.


  • GGK likes this

#12 GGK

GGK

    Vostok 1

  • *****
  • topic starter
  • Posts: 155
  • Joined: 04 Jan 2021
  • Loc: SouthWest Florida

Posted 22 April 2021 - 06:03 PM

https://www.eyepiece..._p/17102024.htm

 

Granted, he's out of stock, but they're pretty good from what I hear.

Thanks.  I saw that one in my search, but never heard of it, so wasn't sure of the optical quality. Looks like no stock at the typical UA vendors.



#13 GGK

GGK

    Vostok 1

  • *****
  • topic starter
  • Posts: 155
  • Joined: 04 Jan 2021
  • Loc: SouthWest Florida

Posted 22 April 2021 - 06:10 PM

I agree, I like the Pentax line very much.  I've use a few lower focal length XLs for years and now also use the 14mm XW.  If Pentax made the XW in ~24mm focal length and 28+mm field stop, I would buy it in a moment.  I thought about the 20mm focal length XW, but the field stop is down to 24mm, so I am giving up TFOV.  If nothing else works out, this is my next best choice, but I also use a 17.3mm Delos with a 21.2mm field stop, and I would like to take a bigger step if I can meet the other criteria - especially the 20mm eye relief.



#14 SeattleScott

SeattleScott

    Voyager 1

  • *****
  • Posts: 11,492
  • Joined: 14 Oct 2011

Posted 22 April 2021 - 06:15 PM

The APM or rebrands is the obvious choice. Xcel LX 25 is cheaper if on a budget.

Scott
  • GGK likes this

#15 GGK

GGK

    Vostok 1

  • *****
  • topic starter
  • Posts: 155
  • Joined: 04 Jan 2021
  • Loc: SouthWest Florida

Posted 22 April 2021 - 06:17 PM

The problem in the 24-28mm range is that the 1.25" barrel is the field stop. At 28mm the most field you can get is about 55 degrees. Its the reason why Pentax stopped making the XL 28 in 1.25"  (55 degrees) and went to the 30mm 2" in the XW 30 (70 degrees). 24mm is a little better but the limit due to the barrel is about 60 degrees in 1.25". No free lunch when optical physics is involved. And getting 20mm of eye relief constricts in more.

Yea, I know.  If I go to 28mm, I will drop in AFOV due to the 1-1/4 barrel limitation.  It's why I think the ES68 24mm hits the limit.  But there's a lot of variations out there and a lot of new stuff I've never seen, so maybe there's another similar option to the ES68 that get's the longer eye relief.  I'm just bouncing at the ceiling of what's physically possible.  The long eye relief need is what's disqualifying most of them.  I like the 70 to 80 degree view best, which is why I didn't jump to a wanted ad for the Pentax 28mm.  Although I read that they were not popular, so there might not be many out there.



#16 GGK

GGK

    Vostok 1

  • *****
  • topic starter
  • Posts: 155
  • Joined: 04 Jan 2021
  • Loc: SouthWest Florida

Posted 22 April 2021 - 06:22 PM

Yeah, I bought the last one from Don lol.gif but would recommend the APM if you can find it anywhere else.

 

I'm using it in a C6 with the same diagonal setup; haven't used it with a reducer yet but am planning to tonight.

I've never used a C6, but I get a lot of mileage out of my focal reducer in my C8.  I think you will be amazed at how different the larger OC's look.  There are many stars to be seen outside the standard view without the FC that give a totally different look to the view.  I understand why many people with a SCT have a second wide field scope.  The right combination of diagonal and 2 inch eye pieces can get my C8 out to 1.9 degrees with an acceptable view, though, so I remain a one-scope owner. Not that I have room for a second scope anyway.



#17 GGK

GGK

    Vostok 1

  • *****
  • topic starter
  • Posts: 155
  • Joined: 04 Jan 2021
  • Loc: SouthWest Florida

Posted 22 April 2021 - 06:40 PM

Vixen 22mm LVW

APM 24mm UFF (or one of the other brands with same optics)

Celestron 25mm XCel LX

Pentax 20mm XW

Baader 22mm and 24mm Hyperions

ES 26mm 62 degree

 

All of the above have long eye relief.  There are other discontinued options on the used market, but these above are all still out there new.  I listed them in order of my favorite to least favorite.  The 25mm XCel LX is the best bang for buck and is also smaller and lighter than most of the other options.  The ES 26mm is small and fairly decent price as well but it's not quite the same quality as the others in my opinion.

Thanks for the list. 

It'd be great to find a Vixen LVW.  I searched for used ones yesterday and found nothing so far. 

The APM looks interesting - I had not known about that one. 

The XCel LX and Hyperion 24mm have shorter eye relief.  Because some that view with me wear glasses, 18.5 to 19 is absolute minimum.

I don't know of a Hyperion 22mm.  I saw the 21 on the Baader website, but the field stop is smaller so doesn't max out the TFOV.

 

I'm considering the ES62 26mm.  It fits the criteria, but most people say I'd be OK at f10, but ugly with the focal reducer.  I have to decide how much I will use the focal reducer with the T-2 prism. 

 

Again, I appreciate the comments.  The replies are confirming that my choices are very limited when I need the long eye relief. 



#18 GGK

GGK

    Vostok 1

  • *****
  • topic starter
  • Posts: 155
  • Joined: 04 Jan 2021
  • Loc: SouthWest Florida

Posted 22 April 2021 - 06:46 PM

Here are all the 1.25" EP's I use. Not all are suitable for what you are using, but this is just part of a much larger workbook.

These are, of course, TVs, but it should be close for other brands as well, I would think.

Two tables, one without reducer and one with.

Hope it helps.

 

attachicon.gif1.25 inch.JPG

Thank you.  I use a few Delos today and the Nagler T4 22mm today because of the longer eye relief.  Other than the Delites, which have lower APOV than the Delos, the only other TV eyepiece I can use is the Nag31, which is too much weight for my little C8.

 

You don't have the 22T4 on your list, but if you ever get the change, look through one.  When back focus within an acceptable range, it's an excellent view and one of my favorites when set up with a 2" diagonal.  With the back focus too long though - right at the end of focus, the outer stars look like Klingon war birds. 

 

Thanks again.


  • wrvond likes this

#19 GGK

GGK

    Vostok 1

  • *****
  • topic starter
  • Posts: 155
  • Joined: 04 Jan 2021
  • Loc: SouthWest Florida

Posted 22 April 2021 - 06:55 PM

We continue to see recommendations for the 22mm Vixen LVW almost a decade after it was discontinued as if there were still thousands of them out there.

I have some recommendations:

24mm Baader Hyperion--not bad at f/10 but not good at f/5.  It has a 28.5mm field stop--the widest in a 1.25".  Long eye relief, 68° field.

24mm APM Ultra Flat Field--better optically and only a tad smaller true field.  Also available as a Meade UHD, an Altair Ultra Flat, a Celestron Ultima Edge and an Orion UltraFlat. Long eye relief, 65° field.

20mm Pentax XW--excellent long eye relief 70° eyepiece, but with a smaller true field than the others.

 

As the focal length exceeds 24mm, the apparent field narrows.

To wit: 26mm (62°), 32mm Plössl (49.5°), 40mm Plössl (40°).  Both have the maximum field for 1.25", but a narrower apparent field.

Starman1, thanks for the reply.  I see your posts elsewhere, so will ask you this question:

 

I see some of the 1-1/4 barrel eye pieces with almost impractical field stop dimensions.  Take the 24mm Hyperion for example.  A 28.5mm field stop means that the barrel thickness in very thin to the point of being easily bent.  The only way I see to get around that is to move the field stop above the shoulder and step out the barrel ID where there's more meat.  This however will mean that the barrel with an ID of probably 27.5 to 28mm will be in front of the 28.5mm field stop.  How will that impact TFOV calculations?  Is this real or are the achieving a clear aperture all the way to the field stop in some way?

 

Thanks for the other brands of the APM.  Is quality equal across the alternate brands?

 

I have the Pentax XW 14 and a few lower focal length XLs and like them.  The 20 XW is an option if I compromise on TFOV, but I also have a 17.3 Delos and I'm questioning if the step to the 20mm XW is big enough or not.  



#20 GGK

GGK

    Vostok 1

  • *****
  • topic starter
  • Posts: 155
  • Joined: 04 Jan 2021
  • Loc: SouthWest Florida

Posted 22 April 2021 - 07:12 PM

I guess I don't understand this argument. Generally, being "all set on" means you already have or are wanting to go to 2" EPs/equipment.

 

And especially in the mid-20mm range all of the wide field options are already 2". And here there are a couple of real standouts:: 25ES100 and the venerable 31NT5, both playing the part of hand grenades when necessary.

Yea, I can see why my request is odd.  I already have and use a 2" dielectric diagonal and use Pentax 30 and 40mm XWs and a 22mm T4 Nagler.  I also use my 1-1/4 eyepieces with an adapter.  My 1-1/4 eyepieces are a mix of Delos, Pentax XW and XLs from 17.3 on down.  I also use this set-up with a focal reducer to get very wide views with acceptable quality out of a C8 SCT.  However, that set-up has extremely long back focus and I lose some contrast, aperture and image quality.  This isn't a real problem when looking at larger DSOs when I really want a wide view.

 

For planets and small DSOs, though, reducing the back focus and moving to a T2 prism diagonal improves the image quality.  I never stay with just planets or small DSOs though.  I tend to bounce around a lot which means that since my highest focal length 1-1/4 eyepiece is only 17.3mm,  I need to either put the focal reducer before with the T2 prism, or change diagonals to use the 22mm Nagler or the 30/40 XWs.  This is just inconvenient - especially when I have guests who want to look at something. 

 

If I had a 1-1/4 eyepiece at maximum field stop, the 0.8 +/- degrees TFOV is enough that I could just swap the eyepiece and not deal with changing diagonals or installing a focal reducer when using the T2 prism.  

 

I thought about using a quick change system to put a 2" eyepiece clamp in place of the 1-1/4 micro-focus eyepiece clamp and using my 22mm 2" Nagler, , but that costs more than simply buying a new 1-1/4 premium eyepiece. Plus the 2" clicklock is almost too big for the T2 prism.

 

I'm just having problems finding the eyepiece that delivers the 70-80 APOV that I like with the maximum field stop, AND the 20mm eye relief.

 

Thanks again!

Gary



#21 GGK

GGK

    Vostok 1

  • *****
  • topic starter
  • Posts: 155
  • Joined: 04 Jan 2021
  • Loc: SouthWest Florida

Posted 22 April 2021 - 07:15 PM

The APM or rebrands is the obvious choice. Xcel LX 25 is cheaper if on a budget.

Scott

I am familiar with the older Meade Series 4000 SWA 24.5mm 67 degree eyepiece.  Do you know that eyepiece and if yes, how does the APM compare with that?

 

Thanks

Gary



#22 wrvond

wrvond

    Mercury-Atlas

  • *****
  • Posts: 2,844
  • Joined: 25 Sep 2014
  • Loc: West Virginia

Posted 22 April 2021 - 07:42 PM

Thank you.  I use a few Delos today and the Nagler T4 22mm today because of the longer eye relief.  Other than the Delites, which have lower APOV than the Delos, the only other TV eyepiece I can use is the Nag31, which is too much weight for my little C8.

 

You don't have the 22T4 on your list, but if you ever get the change, look through one.  When back focus within an acceptable range, it's an excellent view and one of my favorites when set up with a 2" diagonal.  With the back focus too long though - right at the end of focus, the outer stars look like Klingon war birds. 

 

Thanks again.

I didn’t include any of my eyepieces that are 2” or have a 2” barrel. It looks like I didn’t really understand the question in the first place so it doesn’t really matter. lol.gif



#23 cst4

cst4

    Viking 1

  • *****
  • Posts: 704
  • Joined: 06 Jun 2018

Posted 22 April 2021 - 08:26 PM

I don't know of a Hyperion 22mm.  I saw the 21 on the Baader website, but the field stop is smaller so doesn't max out the TFOV.

I meant 21mm

 

An APM 24mm UFF just got posted in the classifieds. It’s serendipitous... grab it before it is gone. I think it is what you are looking for. The only negative is that it is larger than most other 1.25” options but if that isn’t a deal breaker then it’s great. 


  • f18dad and GGK like this

#24 Starman1

Starman1

    Vendor (EyepiecesEtc.com)

  • *****
  • Vendors
  • Posts: 50,280
  • Joined: 23 Jun 2003
  • Loc: Los Angeles

Posted 22 April 2021 - 08:39 PM

Starman1, thanks for the reply.  I see your posts elsewhere, so will ask you this question:

 

I see some of the 1-1/4 barrel eye pieces with almost impractical field stop dimensions.  Take the 24mm Hyperion for example.  A 28.5mm field stop means that the barrel thickness in very thin to the point of being easily bent.  The only way I see to get around that is to move the field stop above the shoulder and step out the barrel ID where there's more meat.  This however will mean that the barrel with an ID of probably 27.5 to 28mm will be in front of the 28.5mm field stop.  How will that impact TFOV calculations?  Is this real or are the achieving a clear aperture all the way to the field stop in some way?

 

Thanks for the other brands of the APM.  Is quality equal across the alternate brands?

 

I have the Pentax XW 14 and a few lower focal length XLs and like them.  The 20 XW is an option if I compromise on TFOV, but I also have a 17.3 Delos and I'm questioning if the step to the 20mm XW is big enough or not.  

The field stop is above the 1.25"barrel.  That means vignetting, though it is small, and it means a lot of in travel to get to focus.

As far as I know, the internals are the same across the brands, though the outside diameters and weights differ due to the different outers.

Unless your scope is a very long focal length (over 2 meters), the jump from a 17.3mm is 30mm in my book.

Think about the magnification jump.  You want at least 50x between low power and the next one up in a 8" scope.


  • GGK likes this

#25 Starman1

Starman1

    Vendor (EyepiecesEtc.com)

  • *****
  • Vendors
  • Posts: 50,280
  • Joined: 23 Jun 2003
  • Loc: Los Angeles

Posted 22 April 2021 - 08:42 PM

I am familiar with the older Meade Series 4000 SWA 24.5mm 67 degree eyepiece.  Do you know that eyepiece and if yes, how does the APM compare with that?

 

Thanks

Gary

No comparison.  The older 24.5mm Meade from the '80s/'90s had a LOT of lateral astigmatism.  It was a copy of the TeleVue Widefield,

which TeleVue replaced with the better-corrected Panoptics (the 24mm APM is on that level).


  • f18dad and GGK like this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: Eyepieces, SCT



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics