[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]
Re: [ATM] 1.25in Versus 2inch focuser.
Marco,
> However in Berry's book it is recommended that in a scope of this
> size, parameters give a practical limt of around 0.5 degrees FOV.
Why worry about field size and so forth, when the real issue is exit pupil
size? Exit pupil is the focal length of the eyepiece divided by the f/# of
the scope. A 31mm eyepiece gives an exit pupil for an f/5 scope of 6.2mm,
which is about the same as most of us have for an entrance pupil. So for
your scope you should have no problem using a 31mm eyepiece. If you buy a
31mm with an 1.25" barrel, you will probably hate it. Get the 2" focusser.
Happy viewing!
John
_______________________________________________
ATM mailing list http://www.atmlist.net/