Re: [ATM] How to test a mirror blank?

[Tom Conlin <tomc@cs.uoregon.edu>]

Hi,
Something to try for viewing internal strain is one polarizer in front 
of the blank and a white LCD computer display behind the blank.
(any blank page will do, LCDs emit polorized light)
It may show up better.


Aaron L Taylor wrote:
> Thanks for the tip about TAS. I'll check them out. I think I went to 
> their observatory once on a public night a few years ago. Are they the 
> group with the white 15" refractor?
> 
> The mirror arrived. I'm pretty positive it's quartz. The density is 
> right and it doesn't heat up when exposed to IR. The object behind it 
> gets pretty hot though, which shows that it's transparent to IR.
> 
> There aren't any chips or cracks or inclusions. However, it did show 
> some strain. Here are some pictures:
> 
> http://www.atmlist.net/contrib/lists-at-subgeniuskitty-dot-com/mirror_strain/mirror_strain_01.jpg
> http://www.atmlist.net/contrib/lists-at-subgeniuskitty-dot-com/mirror_strain/mirror_strain_02.jpg
> http://www.atmlist.net/contrib/lists-at-subgeniuskitty-dot-com/mirror_strain/mirror_strain_03.jpg
> http://www.atmlist.net/contrib/lists-at-subgeniuskitty-dot-com/mirror_strain/mirror_strain_04.jpg
> http://www.atmlist.net/contrib/lists-at-subgeniuskitty-dot-com/mirror_strain/mirror_strain_05.jpg
> http://www.atmlist.net/contrib/lists-at-subgeniuskitty-dot-com/mirror_strain/mirror_strain_06.jpg
> 
> I realize it's hard to see in the pictures but it was kind of tough to 
> see even in person. The only other blanks that I've seen between 
> polarizers either had very noticeable strain or almost none at all. What 
> do you guys think? I'd really like to use it but if that's too much 
> strain, I'd rather send it back and settle for a smaller, but better 
> quality blank.
> 
> Thanks,
>     -Aaron Taylor
> 
> 
> Jarvis Krumbein wrote:
>>  Hi Aaron,
>>
>> There is a very active club in Tacoma, the Tacoma Astronomical
>> Association, which includes a number of active and very experienced ATMs.
>>  Check out their web site at  www.tas-online.org and come to a meeting.
>>
>> Jarvis Krumbein, jkoptic@centurytel.net
>>
>>   
> 
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-- 
           ... nice weather     eh          tomc@cs.uoregon.edu
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