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

[John Vogt <atmer@mail.idt.net>]

K1JJ@aol.com wrote:
> 
> 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 CatheyTom-

Al Nagler once brought me back a Matsuyama 100mm fl. eyepiece from one of 
his trips to Japan. I needed this for a 12 1/2" F/20 Trischief. I owned 
at that time. Cost was about $500.00(1988). Very expensive for a 
Kellner! The barrel was 4" and threaded at the end, FOV was about 50 deg. 
Don't know who you would contact in Japan if interested, tried to fax 
Kasai Trading last week but the number was disconnected.

John