From: "Jerald F. Wright" 
To: Gary Seronik 
CC: atmlist 
Reply-To: "Jerald F. Wright" 




Gary Seronik wrote:

>  I believe the Astroscan has a parabolic
> primary mirror and that the glass plate is simply a window.  (If I remember
> right, this is what Edmund says too.) I took one a part and tested it and
> can assure you that the primary was a paraboloid -- at least in that one.
> (Actually, it was pretty good too, for that matter.)  That's not to say
> they haven't changed the design, but your post is the first I've heard of
> it being s Schmidt Newt.
>
> Gary Seronik

Yep!  I've tested one of those Astroscan primaries and it was the best
parabola I've ever seen.  It wasn't just pretty good.  It was perfect from
perfect edge to perfect edge. No visible or measurable zones of any size at
all. It was too good to hang a number on.  I think it was better than 1/100
wave.
    It is a small mirror but I would be happy to make a surface of any size
that
perfect.  I don't say all this to pump up Edmund Scientific's sales.  But
heck! I know if I wanted to buy an excellent mirror, I know the source of
the only mirror I've ever seen that I couldn't detect an error on.
    I'd like to know how they did it.

Jerry

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