Re: ATM 90mm f-11 APO

["Dan Chaffee" <dchaffee1@mindspring.com>]

Brian Boothman wrote:
 
>I am still in the contemplation stage of this project.
>I was thinking that at only 90mm the glass could not be
>all that expensive. Perhaps I was wrong.
> I was thinking of a refractor because I am limited to
>a small space and the mess associated with a large mirror
>is not an option in my location.

I don't see why a 6" mirror would take noticeably more space
with the project than 90mm of two or three lenses. It would
out perform it in every way except image stability and blackness
of background. If you're cleaver enough or copy someone else
who is, you can make a 6" f/6 newtonian shorter in storage than 
any 90mm apo I've seen.

I'm building a  refractor too, but if I were to do one
that small, a say,  f/14  90mm crown/flint doublet would be so
close to unobtrusive color that an "ED" or fluorite combination
wouldn't be warranted in my book. Much cheaper too. If
this is your first optics endevour, I recommend staying away 
from expensive glasses.

D. Chaffee