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

Eyepieces SCT
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#26 MitchAlsup

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Posted 22 April 2021 - 09:16 PM

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.  

But you get a 1.2º FoV with the 2" stuff.......



#27 GGK

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Posted 22 April 2021 - 10:47 PM

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

No, you were actually on target with the 1-1/4 eye pieces.  That's what I'm looking for.  I just didn't recognize that all on the list were, if fact, 1-1/4.  I need to have 20mm or greater eye relief.  I think the Delos and Delites are the only TV 1-1/4 models with eye relief that long.  Since I presently use Delos and like them, I started this search on the TV website.  I just didn't find any others.  That's really been my difficulty in this search - that long eye relief.

Thanks, though.  I appreciated the replies.


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#28 GGK

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Posted 22 April 2021 - 10:53 PM

Unbelievable timing. 

 

As CST4 posted above, an APM 24mm UFF eyepiece appeared on the classifieds as were were all discussing this.  I saw it and was fortunate enough to be the first responder and bought it.

 

I would not even have know what it was if is wasn't for all of your comments.  

 

Again - Thanks you all very much!

 

Gary


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#29 GGK

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Posted 22 April 2021 - 11:04 PM

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.

That's what I thought on the field stop location.  With the minor difference between clear aperture in the barrel and the field stop diameter, I personally would never notice the vignetting unless maybe the APOV was very narrow.

 

For the mag steps, I agree with you under normal circumstances.  For my case, I am just looking to maximize the field of view with a 1-1/4 eyepiece, but still keep the APOV as wide as possible.  The 24mm it the focal length where the math works.  Not many 20mm eye relief options, though, which is why I was asking the CN team.  When I need greater exit pupil for more light, I move to the larger diagonal and 2" eye pieces. 

 

Thanks, again.  Very helpful.



#30 GGK

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Posted 22 April 2021 - 11:14 PM

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).

Good to know. Thank you.  I suspected as much from both new and used prices.  



#31 Virtus

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Posted 23 April 2021 - 07:49 AM

Unbelievable timing. 

 

As CST4 posted above, an APM 24mm UFF eyepiece appeared on the classifieds as were were all discussing this.  I saw it and was fortunate enough to be the first responder and bought it.

 

I would not even have know what it was if is wasn't for all of your comments.  

 

Again - Thanks you all very much!

 

Gary

You got a good deal and I think you'll be happy with it.




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