Re: [APML] Focus stability and carbon fiber tubes

["Bobby Middleton" <bobm@koyote.com>]

Dave I have the same instrument as Steve; the Tak BRC 250. Ours (as opposed
to the newer models) have the carbon tube and yes they are indeed a pleasure
to work with. Sct's are especially prone to temp induced focus shifts
because of the high secondary amplification. When i imaged with an LX200 I
had to refocus after each exposure and sometimes that wasn't enough.
Bobby Middleton

----- Original Message ----- 
From: "Steve Walters" <s-walters@comcast.net>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Sunday, April 25, 2004 8:13 AM
Subject: Re: [APML] Focus stability and carbon fiber tubes


> Dave,
>
> It really does matter. I don't have the C9.25 but every alum tube I've
ever
> used shifted focus in very noticeable ways. You will be restricted to
> imaging only when the temperature is stable.
>
> It's worth the hassle.
>
> Steve...
> www.StarryNights.us
> astrophoto@comcast.net
>
> ----- Original Message ----- 
> From: "David Ebbecke" <deebbecke@yahoo.com>
> To: <astro-photo@seds.org>
> Sent: Sunday, April 25, 2004 7:26 AM
> 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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>
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