Re: ATM 3" 75mm or 4" 100mm eyepieces

[K1JJ@aol.com]

In a message dated 96-08-20 00:24:45 EDT, you write:

>
>>  Say you had a 10" diameter 245mm eyepiece giving a mag of 18X and exit
>pupil
>>  of 30mm!  What would the view look like here with a Kelner?
>
>This one is fairly easy to check yoursef. Get a ~50mm f.l eyepiece and
>put it behind an f/1.4-1.8 camera lens. The difference between what you
>see in that arrangement and what you would (or wouldn't, to be more
>precise) in your Newtonian with 250mm f.l. eyepiece is that central
>obstruction will be big enough to COMPLETELY cover your eye's pupil,
>i.e. you will see nothing.
>


Bratislav:

Ahhh....Nows that's what I was looking for!  Ya know, I do remember that
central obstruction effect when trying various "camera lens" as an
experiment, and seeing the BIG secondary floating around in the field!

Also the analogy of only using 9 inches of the 22" mirror also hits home.

In fact, it seemed with a smaller 10" F5 Newtonian (55mm Plossel eyepiece)
the view had almost a "television " look to it where the eye relief was about
1.5" and you could actually see like looking at a camcorder screen...I think
you know what I mean. For a real trip, try this with  8"-10" Newtonian
binoculars sometime.

Think I'll use some of the other ideas posted also concerning various
sources, and limit it to a 75-80mm 3" eyepiece now.

Anyone know how to get ahold of Joe Sunseri or John Dietch?

Also ANYONE hearing of a CLEAR aperature  (3"-4" diameter)  75-100mm eyepiece
please let me know! It will save the trouble of re-inventing the wheel here.


Thanks.

Tom Cathey