[ATM] Re: 40" mirror

["Mike Conran" <mike@guidesys.com>]

Oh, if the scope is going to be more or less permanently mounted, some of 
the weight issues become less of an issue.
Mike Conron 

Jerry B. Hillman writes: 

> 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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Mike Conron 
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