Re: ATM 13" SCT project

[RDuvall@pixworks.com (Robert Duvall)]

At 6:51 PM 2/12/97, Robert  C. Pfaff wrote:
>Hi Everybody
>
>I just started my 13" f 12 SCT project. As we speak I am grinding
>the back of the primary flat. Then I only need to make 4 optical
>surfaces, core drill 2 holes and machine all needed cells, baffles,
>and a focuser and I am done ;-)  Well some of us ATM's must be NUTS ;-(
>
>Anyway I will keep the list informed on my progress or non-progress
>as I go along. I have no web page but I will take pictures as I go
>along so SOMEDAY thay can be viewed at a web site.
>
>If anybody on this list has made a SCT please respond.
>
>Another crazy ATM
>Bob Pfaff
>Torrance, Ca

Well 20 years ago I read Tex and decided to core my 12.5" mirror for the
Cass I'd make someday. I got sidetracked for 19.5 years after finishing
grinding. I guess pitch laps scared me off. Now I'm finishing parabolizing
the mirror.

It's much tougher since I cored all the way through. My plug lasted through
grinding, but fell out when I started polishing this 19.5 years later.
Still, when pressing, the pitch was moving into the cut area around the
core, so I've removed the core plug and removed the center of the lap also.
I'm experiencing turned down edge there now. If you can keep within maybe
an 1/8th of the front surface (after grinding) , maybe you could avoid
stress relief changes and have an easier time figuring.

How I thought I would make and test the secondary, I don't know. Well,
actually, I was living in Rochester NY at the time and had access to the U
of R optics lab as well as George Keene at Kodak, so I guess I do know. I
should have finished it then!

If you have success, maybe I'll finsih mine! I have a computer driven mount
and CCD camera to make first.


Robert Duvall

Software Engineer,
Amateur Astronomer (Telescope Nut),
Guitarist/Songwriter,
and General Scientist (according to my son)

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