From: "Pat Bunn" 
To: 
Reply-To: "Pat Bunn" 


I started a planetary scope mirror about ten years ago and got it to the
late stages of smoothing before getting discouraged with having to build a
tester and the seemingly complicated polishing and figuring. I am now ready
to build a tester ( I have cut out all the woodwork for the Stellafane
tester) and finish the mirror. The problem that I have is to identify the
place that I stopped at. I remember measuring the focal length with a light
and a wet mirror and testing the reflection of  an incandescent bulb (per
Texereau who I used as a guide to grind the mirror ) as a test for
smoothness. How can I determine that I finished the smoothing and the
mirror is ready for polishing? Any help would be appreciated.

Pat Bunn


----- Original Message -----
From: "Jerry B. Hillman" 
To: 
Sent: Wednesday, July 02, 2003 7:53 PM Subject: ATM secondary mirrors


>
> Hi all,
> Vladimir has challenged me to make the diagonal for this mirror. Actually,
> he questioned why I am buying one rather than make one.  Having read
horror
> stories of how hard it is to make a diagonal, I had more or less decided
it
> wasn't worth the effort.  Now, having thought about it all day, and doing
> internet research on the subject, I am asking myself, Why not??
> I have some 5/8" thick glass that is the top of a small side table.
> Considering how expensive good diagonals are, and considering I can have
it
> coated at the same time I coat my primary for no additional cost, it makes
> sense to give it a try. I'll wind up with a better one than I can buy
> anyway, and without any additional cost to myself. I already have all the
> necessary grinding and polishing supplies, and the glass to boot.
> I'll be star testing the scope again tonight, so I'll have a chance to do
> the Ronchi test also.  I am going to spend some extra time to make sure
the
> scope is properly collimated (Thank you Nils Olof Carlin for a very
> informative desertation on the subject ) and check everything else I can
to
> make sure all is in proper working order. I highly recommend Nils FAQ on
the
> subject of collimating a telescope. It makes things very clear on the how
> and why of collimating a scope.
> Clear skies, Jerry
>
>
>

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