Re: [ATM] ritchey cretians

["Mitchell R" <funnybone101@embarqmail.com>]

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
Khail Rosenberg
Sent: Saturday, January 19, 2008 12:22 PM
To: Bob May
Cc: atm@atmlist.net
Subject: Re: [ATM] ritchey cretians

Hi Bob,

I have an ambition to never use machines to make my mirrors, but i think
something for this size, i really will have no choice... I think i will make
a few machines, will help if i want to make something bigger and better..

And i have read about the diamond pads, you are right, even though grit can
be relatively cheap, with such a large mirror i feel i will spend more on
grit than the actual glass itself..

Any advice on machines to actually lift and put it on stands? I do
understand the concern of dropping the mirror, it will make a lot, a looooot
of work really out the window...

Any advice on griding or polishing, and then testing both primary and
secondary will be greatly appreciated.

I believe my course of action will be as follows:

1. Make the 48" glass x 4"
2. make the machines to grind the bad boy... any suggestions on HP for the
motor? 20, should be ok?
3. get three flats made for testing all 48" x .75", i chose this because it
can be made for a pretty darn good price, any comments on the thickness
being too thin?? .75 is ok?
4. ASK ATMLIST.NET where to go from there.. after I already have a ground
out mirror and one thats already polished to a sphear.. where to go from
there??

..... any good step by step plans on the entire process I will be happy to
donate many goodies to a convention, person, school etc...

Thanks,
Mikhail



     Just a few quick ideas. For getting the mirror from machine to test you
could build your test stand to tilt from flat to *near* vertical and somehow
"push" the mirror from the machine right onto the stand if they are the same
height.

	Also, 4" thick will weight a heck of a lot. I believe you said you
can pour your own glass? You could try cellular if you wanted, like these

 
http://www.embeddedrf.com/Lookinglass_Webpage_Files/Webbed_Backed/Webbed_Bla
nk.html

They go up to 48" sizes on that website. Or just a little thinner solid
blank perhaps.

Good luck!! I too hope to make a mirror "around" that size someday (my
experience thus far consists of 3 mirrors between 4.5"-10" and F/ratios of
3.8-6.5) so still some way to go!

Mitchell

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