Baader Hyperion-Aspheric 31mm modular EP - daft question

[JOC]

Baader Hyperion-Aspheric 31mm modular EP (72")

OK, I've got one of these and kind of forgot I had it.  Needless to say I don't think I've been out with it yet.  Although it might seem a daft question, if I can dismantle the focuser to hold a 2" (which I can on my scope), is there any point in bothering to if I happen to have a load of other 1.25"EP's to use at the same time.  i.e. Will the view be significantly improved, and would it therefore be worthwhile, to use it with the 2" mount if I can (the ends unscrew and you add 1.25" or 2" adapters).  Also, it is clearly going to be a low 'magnification' (x8), wide field of view weapon I'd appreciate it if anyone could give me a couple of targets that would really benefit from it.  Many thanks

[Ruud]

The eyepiece will vignette in a 1.25" adapter.

The need for 2" over 1.25" is to make room for the field stop, not to improve image quality. You need 2" for low magnification eyepieces with wide fields of view. An eyepiece shows a magnified version of a circle of the image that is projected by the telescope's objective. The image circle that a 31mm 68° eyepiece wants to show is bigger than what will fit in a 1.25" barrel.

[John]

I had one of these for a while. As said above, with the 1.25" barrel in place the AFoV is reduced to around 55 degrees. Wide for a 1.25" inch but less than the 2 inch barrel will allow. Performance quality was affected when the 1.25" barrel was in place insomuch as the field that was visible was better corrected (ie: less astigmatism) at the edges than when the eyepiece is has the 2 inch barrel attached.  In "full field" mode (ie: 2 inch barrel in place) I could see quite a bit of astigmatism around the field stop.

 

[JOC]

Interesting so this response below suggests that the lower power will benefit from the 2" setup

1 hour ago, Ruud said:

The need for 2" over 1.25" is to make room for the field stop, not to improve image quality. You need 2" for low magnification eyepieces with wide fields of view. An eyepiece shows a magnified version of a circle of the image that is projected by the telescope's objective. The image circle that a 31mm 68° eyepiece wants to show is bigger than what will fit in a 1.25" barrel.

but the view at 2" might suffer more at the edges from astigmatism (the verticals or horizontals will disappear - if it's the same error as my specs correct for my eyesight) than if the 1.25 setup is used as per this reply:

8 minutes ago, John said:

I had one of these for a while. As said above, with the 1.25" barrel in place the AFoV is reduced to around 55 degrees. Wide for a 1.25" inch but less than the 2 inch barrel will allow. Performance quality was affected when the 1.25" barrel was in place insomuch as the field that was visible was better corrected (ie: less astigmatism) at the edges than when the eyepiece is has the 2 inch barrel attached.  In "full field" mode (ie: 2 inch barrel in place) I could see quite a bit of astigmatism around the field stop.

There is more to this question than I expected!

[Louis D]

10 hours ago, JOC said:

Interesting so this response below suggests that the lower power will benefit from the 2" setup

but the view at 2" might suffer more at the edges from astigmatism (the verticals or horizontals will disappear - if it's the same error as my specs correct for my eyesight) than if the 1.25 setup is used as per this reply:

There is more to this question than I expected!

There's no mystery here.  Just about any eyepiece benefits from having a narrower field stop to mask off a poorly corrected edge.  Since you've got the eyepiece in hand, try it both ways to see which way you like better, and let us know. ?‍♂️