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

[Aaron L Taylor <lists@subgeniuskitty.com>]

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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