[ATM] Re: Second Thoughts on Mirror Support

[jonah at eecs.berkeley.edu (Jeff Anderson-Lee)]

I have a friend who makes telescopes professionally.  He uses RTV 
following years of experimentation.  It works better than other 
alternatives when done correctly.

Jeff

Jarvis Krumbein wrote:

>If I remeber correctly, the Magellan mirror is also actively supported
>which requires a real connection (positive attachment)  with the mirror
>section  being controlled.  Therefore, this is not a valid example.
>
>Jarvis Krumbein
>
>On Sun, 8 Feb 2004 19:28:27 -0600 "Ken Hunter" <kb7h@onemain.com> writes:
>  
>
>>----- Original Message ----- 
>>From: "Stuart Hutchins" <stuart452@earthlink.net>
>>
>>    
>>
>>>Any sort of  "positive attachment" violates the fundamental 
>>>      
>>>
>>requirement of
>>    
>>
>>>"flotation".  That 's why you hear all the howling when you say 
>>>      
>>>
>>RTV.  No
>>    
>>
>>>professional grade instrument with a solid mirror uses glue to 
>>>      
>>>
>>hold it down.
>>    
>>
>>Hmm...
>>
>>Better tell that to the Mirror Lab folks at the University of 
>>Arizona... they're
>>using RTV to hold the 8.4 METER Magellan mirror to the loadspreaders 
>>and
>>I'd surmise that the Magellan is a "professional grade instrument"
>>
>>http://medusa.as.arizona.edu/mlab/lbtcast.html
>>
>>Additionally, many observatories are using RTV to hold fairly large 
>>secondary
>>mirrors to their supports.
>>
>>All this "chit-chat" on what's possible and what's doable fails to 
>>take into
>>account that the average seeing conditions are going to be several 
>>magnitudes
>>worse than the deflections seen (or computed and not seen) in these 
>>scopes.
>>
>>I agree that one should make their scope to the best of their 
>>ability but now
>>that we have computers to tell us what we've been doing for so long 
>>is not
>>going to work now... maybe we should give up making telescopes and 
>>move
>>on to becoming the servant of our computers and all those small 
>>numbers that
>>don't mean anything in real life.
>>
>>What do you want to do, build a scope or worry about tiny 
>>nonsensical numbers?
>>
>>Ken Hunter
>>
>>
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>>
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