making a 8" mirror

Hi,
I am a college student and I am considering making my own mirror, I was
wondering how hard it would be to create a 8" F/5 mirror from a pyrex
blank, I understand that it would take a great deal of time, but is
there a good chance that I could never do it?

-Aaron Smith

heywood floyd wrote:
Hi,
I am a college student and I am considering making my own mirror, I was
wondering how hard it would be to create a 8" F/5 mirror from a pyrex
blank, I understand that it would take a great deal of time, but is
there a good chance that I could never do it?

You should be able to. Some web sites:

http://astro.umsystem.edu/atm/

http://home.clara.net/smunch/tele3.html

http://www.argonet.co.uk/users/drmac/Scope/theory.html

http://members.shaw.ca/fvas2/

And there are many more.

Phil

heywood floyd wrote:

Hi,
I am a college student and I am considering making my own mirror, I was
wondering how hard it would be to create a 8" F/5 mirror from a pyrex
blank, I understand that it would take a great deal of time, but is
there a good chance that I could never do it?

-Aaron Smith

I would go f/D=6 because f/D=5 is tough for a first mirror. Actually
f/D=8 is a nice first mirror while f/D=6 can get crazy at the end. I
think that Jean Texereau's "How to Make a Telescope" is very hard to
beat. Look it over. His instructions work. You need to be mechanically
handy. You need a clean work area. Grinding through fine grinding could
be done in a day but most of us couldn't do it in a day. A week to two
weeks is fine. You can use fast polishers like cerium oxide. You can get
a really nice seeming polish in maybe 8 hours or less. Finish polishing
with rouge. Polish with rouge until the orange peel in the foucault test
goes away. Figure with rouge. Don't give up when it takes 50 hours or
100 hours or 200 hours to figure. It takes a while to learn what the
glass does. First mirrors are like that.

If you consider your labor free and the idea of making a mirror appeals
to you then do it. It can be fun and you can point with pride at your
workmanship.

Chuck
P.S. Some say that you can test a Pyrex mirror 2 to 4 hours after doing
a figuring operation. I was not pleased with this and found work
proceeded better if I allowed 6 to 8 hours before testing. The longer
the better.
--
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons

It took me about 40 hours of work to do my first mirror. That was a 8" F7.5
and I did a very nice job. The boring parts are getting the hole dug in the
beginning and polishing the mirror before figuring it.
There are a lot of websites that describe grinding and polishing mirors and
a quick search on Google will show a whole bunch.
The 8" size is a nice size to start with.

--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works evevery time it is tried!