Re: [ATM] 50 mm FL 1 1/4 " eyepiece

["Stephen Koehler" <s.c.koehler@gmail.com>]

Ulhas,

On 6/5/06, Ulhas Deshpande <ulhas_ngp@sancharnet.in> wrote:
>  I am looking for a 50 mm fl  eyepiece to fit 1 1/4 inch drawtube. I am unable to find one on the net. Can anyone help

You are unlikely to find one.  The maximum field stop of a 1 1/4 inch
eyepiece is about 30mm.  Let's say your 50mm eyepiece was a Plossl
with a 50 degree aparent field of view.  That would require a field
stop of 46mm, which would fit within a 2 inch eyepiece barrel, but not
a 1 1/4 inch barrel.  To accommodate a 1 1/4 inch barrel, the eyepiece
would have to have an extremely narrow field of view, which defeats
the purpose of a low power eyepiece.

Looked at the other way, let's say you want to find the longest focal
length Plossl that works with a 1 1/4" eyepiece and gives you the full
50 apparent field of view.  The result is a 32mm Plossl.

-- 
Steve Koehler
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