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

[Jason Ware <jtw@galaxyphoto.com>]

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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-- 
 -Jason Ware 

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