Re: [APML] co-efficient of expansion for 10" SCT

[Duncan Munro <dmunro@sfu.ca>]

Hi. I'm measuring the focus shift at the focal plane. M. Hart and Doc G. 
were geting .15mm per .6 deg C. with a 10" F10., or .25mm per deg C. I'm 
getting .15mm per deg C. which is consistant with the lower 
magnification of the F6.3 secondary.

cheers

Duncan


Jason Ware wrote:

>What are you measuring? The tube or the focus shift.
>The secondary magnifies the effect of the expansion.
>
>Alan Voetsch wrote:
>  
>
>>Hey Duncan,
>>
>> Doc G. is probably the guy most likely to have done this. You could
>>try posting your question on MAPUG to see if he, or someone else has an
>>answer for you. I do remember that he had even gone as far as measuring
>>contraction/expansion OTA potentials from the nearby heat of a human
>>body on a cold night.
>>
>>Alan
>>
>>--- Duncan Munro <dmunro@sfu.ca> wrote:
>>    
>>
>>>Has anyone calculated the co-efficient of expansion for a 10" SCT?
>>>I've done some rough  testing with my 10" F6.3 OTA and I'm getting
>>>about
>>>.15mm per deg C.  Does this sound plausible?
>>>      
>>>
>>SCT Astrophotography: http://www.pbase.com/avoetsch/astrophotography
>>FS-102 G-11/Gemini: http://www.pbase.com/avoetsch12952/tak_fs102
>>& http://www.pbase.com/avoetsch12952/fs102
>>& http://www.pbase.com/avoetsch12952/takpf
>>
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>
>  
>

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