OK, so apparently my original post wasn't clear enough for some so let me try again.
- I have a 10" f/5.4 Dob.
- It's equipped with a zero power finder and a 50mm optical finder
- The optical finder provides about a 3.7º actual field of view
- That optical finder is used at 22x. I can't go much lower in power due to my astigmatism
- I don't use glasses when I observe. When I observe (take note of that)
Problem: Some objects are a bit too faint in that optical finder making it difficult to be sure that I've found them.
I'm thinking that since my main scope pulls in much more light than the optical finder, maybe I can use it as a finder.
The requirements for this to work for me would be...
- I need an eyepiece that gives me the widest field possible (so 2")
- Large enough eye-relief so that I can use my glasses.
"Wait", you say. "You said you don't use glasses when you observe"
Correct. Observing means (to me at least) spending a long time at the eyepiece studying an object. For finder purposes it's only a minute or less. Further, I know that an eyepiece that would give me the wide actual field that I need, would have an exit pupil well beyond the point where my astigmatism kicks in. I don't want to spend the $$ for another Dioptrx and the $$ for the eyepiece that it is compatible with just for the brief time I'll be using this "finder", thus my desire for an eyepiece that I can see the whole field through when using my glasses.
I know there are a lot of cheaper, simpler design, 2" eyepieces, 30mm or longer, that would fit my requirements. All I'm asking is, of all of these, has anyone found one that seems to be better than the others in terms of correction.
Now read this next part carefully...
I don't expect great correction near the edges. Given my fast focal ratio and the level of optics that I'm asking about, I'm OK with that. After all, I don't need pinpoint stars but rather just the ability to see stars and to distinguish between stars and DSOs. But some eyepieces may be better than others.
So, again, of all the options out there, does anyone have an opinion (based on first hand use) of which might be the best.