[Aavso-photometry] Used CCDs

[Tom Krajci]

>From: cspratt <cspratt at islandnet.com>

>I was looking at a used  SBIG 237A CCD which is light in
>weight but doesn't have a guiding chip (do I need one?).

Depends on how well your mount/drive perform...and what kind of work you do.

I do 6-12 hours of time-series of one target...1000+ exposures in one night.
I need an autoguider to stay on target...and so I can sleep!

If you only do photometry while you are at the scope, and only take a few
exposures, then move to the next target...you probably don't need an
autoguider.

>I have an AP600E
>GOTO mount which can handle up to a 9.25" SCT. But this is a portable
>setup and takes time to calibrate the guiding chip, thus I wouldn't use
>the guiding chip in any case.

You don't need to calibrate the guiding chip every time you set up.  I bet
your drive motors work at the same guiding/correcting speed night after
night.  Mine do.  Just orient your autoguider the same way every night...and
you can reuse your calibration info in your autoguider software.

I'm a fan of temperature regulated CCD's...choose a temp. set point your CCD
can hold all night for a given season...shoot your calibration frames (bias
and darks) on a cloudy night...reuse them all season.  (You only need to
worry about flats each time you set up...and if you use a light box...you
can shoot the flats at any time, and not depend on that 'window' of
twilight.)

Good luck!

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Tom Krajci
Cloudcroft, New Mexico
http://overton2.tamu.edu/aset/krajci/

Center for Backyard Astrophysics (CBA)
http://cba.phys.columbia.edu CBA New Mexico

American Association of Variable Star
Observers (AAVSO): KTC http://www.aavso.org/
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