Scope Eyepiece diameter for old eyes

[DaveC426913]

TL;DR Summary

Are 2" eyepieces easier on aging eyes?

I have a friend who wants to replace his scope. Has a balcony overlooking the lake, so less about stars; more about Moon and terrestrial. So he's interested in a (right side up) refractor. He can save on the mount by getting an alt-az instead of an eq.

He's looking at this 4" Celestron:
https://www.amazon.ca/dp/B014EQ1LB2/

I've never explored 2" eyepieces. Would that be something that aging eyes would find easier?

Though 2" EPs are expensive, he probably only needs one.

His budget is $500. Is a scope with 2" EPs out of range? Would a 1.25" scope with an 2" adapter work? Is there such a thing?

 

[Drakkith]

Two-inch eyepieces have an advantage in that they allow for a larger field of view, but that's it according to my limited understanding. If nothing else, I'd recommend a long eye relief eyepiece to make extended viewing sessions easier. But with a budget of only $500, including scope and mount, there's not a lot of choices available for eyepieces.

He's looking at this 4" Celestron:

Honestly, given that he's interested in mainly terrestrial viewing, I'd recommend a good quality 'spotting scope' with an adjustable zoom eyepiece. They are versatile, easy to setup and use, and uncomplicated.

Would a 1.25" scope with an 2" adapter work?

Probably not. The reason 2-inch eyepieces work is that the field stop, the thing that determines the maximum FOV, is often part of the eyepiece itself, and a larger field stop allows for a larger FOV. At least when the focuser tube and eyepiece are matched in size or the eyepiece is smaller. However, if you put a 2-inch adapter into a 1.25-inch focuser, the focuser tube itself might then become the field stop since it is so much smaller than the eyepiece tube. In other words, the focuser tube might be blocking rays that would otherwise pass through the field stop of the eyepiece, rendering the larger eyepiece size irrelevant.