RE: [APML] Focus stability and carbon fiber tubes

["Gene Horr" <genehorr@houston.rr.com>]

Well, it will matter but don't count on having zero CoE.
Regular CF tubes while having a CoE less than aluminum
do shrink with cooling.  IIRC while the fibres don't
shrink that much the resin does.

To produce a true zero CoE tube is supposedly not a cheap
process as you have to mix in materials with an offsetting
negative CoE.  I doubt that the mass market SCTs go to
this expense.

But all in all I would still personally go to the trouble
of getting what I had paid for.  Even if provides only
a 50% improvement that still doubles your exposure time.

Gene Horr
genehorr@houston.rr.com


-----Original Message-----
From: astro-photo-bounces@seds.org
[mailto:astro-photo-bounces@seds.org]On Behalf Of David Ebbecke
Sent: Sunday, April 25, 2004 6:26 AM
To: astro-photo@seds.org
Subject: [APML] Focus stability and carbon fiber tubes


I recently ordered a C-9.25" carbon fiber XLT.  What
arrived however was the aluminum tube.  I went with
the carbon fiber specifically for astrophotography
work because of what I've read regarding its thermal
stability hence greater focus stability .  None of the
posts I read were recent nor was there consensus. 
Wonder if anyone could share their knowledge on this
topic.  I could exchange the tube but would rather not
go through the hassle if it really doesn't matter. 
I'm currently doing digital SLR work (4-5 minute
ungiuded stacked exposures) with a 4" refractor and
wanted the C-9.25" to go a little deeper.  Thank you
in advance.

Dave Ebbecke 


	
		
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