Long focus, Wide angle Eyepieces

[Chriske]

Hi guys...'m new here in this section.

Our group is busy building a few(6) Delmarva Schiefs.
The scopes we're building will be 108mm f/29(about, still busy grinding the optics)
We all have 'a bunch' of eyepieces from older projects and want to buy one more. The reason for that 'one more' is we want to see the entire Moon in the FOV using a 1"1/4 eyepiece.

So we need a wide angle eyepiece with a long FL.
Assuming the scope has a FL of 3100mm and using this eyepiece we have a magnification of 125x
That gives us a true field of 0.51°, so about the size as the Moon.

In the eyepiece 'world' there are a few other candidates to do the job, but they're rather expensive.
Does anyone now were to buy other long focus 1°1/4 eyepieces with an even larger AF...?

Thanks...

Edited January 12, 2023 by Chriske

[AstroKeith]

You are limited by the field stop diameter in 1 1/4" eyepieces. That one you linked to is about on the limit. Laws of physics!

[Louis D]

If you have enough in-focus, it is possible to put a larger than 27mm field stop above the insertion barrel, but you will have some edge of field vignetting.  The vintage 35mm Celestron Ultima took this approach.

I've also held my 27mm Panoptic's 2" insertion barrel around the 1.25" receiver barrel with the thumbscrew removed, and it worked quite well visually.

[Chriske]

Hey...!

What about this one...?

 

 

Edited January 12, 2023 by Chriske

[Louis D]

Same 27mm field stop as a 32mm Plossl or 24mm APM UFF, just with a narrower apparent field of view because the same image circle is presented at a smaller image scale due to the lower power.

Why not just redesign your scope to be compatible with 2" eyepieces if you want a wider field of view?

[Chriske]

redesigning, well we discussed it and a 2" eyepiece is a bit overkill for a scope this 'thin' we think.

[badhex]

I would say the same as @Louis D- giving yourself the option of 2" EPs opens up a lot more possible choices such as the Lacerta ED 40mm. 

[Chriske]

Ordered a 40mm Omni from Celestron, just one to see how it performs.