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Re: [ATM] [atm] how to test flat secondary mirror
Interesting question.
Flats are generally tested using a reference flat, that is another flat
known to be flat to a specific tolerance.
The reference flat is put on bottom, the flat being tested is put on top,
with the fface being tested in contact with the reference. A monochromatic
light is shined on the pair and interference fringes or Newton Fringes are
shown. The straightness of the Newton Fringes will show how close your test
surface is to your reference surface. There are many books that will show
you how to conduct this very basic test as well as how to make a tester.
Amateu Telescope Making II has an excellent section on making optical flats,
as does Norman Reimer's book, Making a Refractor Telescope. This book was
recently published and is available from Willmann Bell, www.willbell.com
Now, It's our turn.
I have not noticed any previous posts from you on the list, and from the
time stamp of your post, I presume that you are not in the USA. I am
interested in hearing about your telescope project, and what types of
telescopes that you may already have. Would you please tell the list about
yopur telescopes and projects as well as a little about yourself?
Kind regards,
Francis J. O'Reilly
Brewster, New York, USA
----- Original Message -----
From: "seyyed mahmoud ghasemi" <modeler72@yahoo.com>
To: <atm@atmlist.net>
Sent: Sunday, August 19, 2007 1:13 AM
Subject: [ATM] [atm] how to test flat secondary mirror
> dear sirs,
>
> would you please guide me how to make and polish a flat mirror and
> how to test ( if it is exactly flat ) for secondary mirror
>
> i appreciate your guidance in advance
> faithfully yours,
>
> s.m.ghasemi
>
>
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