Re: [ATM] 40" mirror

["Jerry B. Hillman" <JBHillman@ev1.net>]

Hello everyone,

The biggest argument against my 40" x 4" mirror keeps coming back to
cooldown issues.  Matt is right that now is the time to solve those issues
rather than after casting the thing.  I have had several suggestions on how
to fabricate it as a honeycomb back mirror and I am currently talking with
Richard about possibly making it a ribbed mirror.  I am not objecting to
making it lighter.  I just don't want to make it weaker.  As sure as
anything else, if it is prone to astigmatism or potato chipping due to its
thickness, then that will happen and ruin this entire project.  The scope
isn't intended to be a star party scope, unless people want to come here. It
will have a home in it's own observatory in my pasture. There I can control
the temperature and can put in additional temperature controls specifically
for the mirror.  As far as balance.  Adding weight to the base doesn't
necessarily mean I have to add weight to the upper cage to balance it.
Shifting the altitude bearings a little can move the COG an amazing amount.
Controlling the pressure on the altitude bearings can help compensate also.

As far as the mirror itself, I'll keep the list posted on developments
concerning the thickness and ultimate design.

Clear skies, Jerry

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