Re: ATM Replica mirrors?

[Robert Duvall <rduvall@jlc.net>]

At 1:55 PM -0200 8/30/98, Diego Alejandro Protas wrote:
>Yesterday I found this page, http://www.abwam.com/opticast/index.html,
>while surfing the web. They are selling mirrors made of cast gysum cement
>substrate covered with thermoseting plastic. They claim 1/4 p-v accurracy.
>
I have one that's about 1/3 wave, maybe 1/2. It's fine at low powers (under
30x per inch). Actually does well compared to my own 1/8 wave mirror on an
average night. They suggest dissicant when not in use, and I'm watching
this for signs of degredation with time. So far, so good (6 mo).

>
>Is this good enough for an astronomical mirror?

Generally yes, about as good as many commercial systems I've looked through.

>if so, this kind of mirrors would be excelent for building a low cost
>"introductory/educational" mirror.

Yes, it is good for that. A good beginner scope.

>maybe we can do it ourselves?

Not likely. From studying the one I have, there's several layers, not of
smae material. And reading his patent convinces me this was no simple feat.



Robert Duvall
Force5 Telescope Making Resources

Software Engineer, Amateur Astronomer (TN),
and General Scientist (according to my son)
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