Re: [APML] 500mm mirror lens as a guidescope?

["DEREK BAKER" <derekb@sympatico.ca>]

I have heard stories of the lens elements shifting over long exposures, both
laterally, and in terms of focus. If your shots were just 10 or 20min,
then....

Derek

----- Original Message -----
From: George Anderson <georgea@cam.org>
To: APML <astro-photo@seds.org>
Sent: Tuesday, September 02, 2003 10:57 PM
Subject: [APML] 500mm mirror lens as a guidescope?


> While messing around with getting my B&W quickcam autoguider working and
> starting to worry about focuser flexure on my el-cheepo guidescope I
> started wondering (dangerous habit)...
> For widefield shots with a 35mm camera (50mm lens or less) would a
> guidescope with a 500mm focal length be sufficient?
> The 500mm f/8 mirror lens I have is very lightweight and has no
> detectable barrel flexure. The effective aperture is only 62mm but that
> is only a touch smaller than my 70mm f/10 scope that I use for manual
> guiding.
> Any thoughts from those in the know?
>
> George Anderson
> Montreal Canada
>
> Clear skies and good health
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