Re: [APML] Measuring Sky Background With an ST-4

["Jim Janusz" <jjanusz@dc.rr.com>]

Thanks again everyone.......

I want a simple way to compare dark sky sites without having to set up a
scope and camera.  I think this will give me what I want.

Dave, good to hear from you again, it's been too long.  What new type of
astrographs have you been conjuring up?  Still shooting film or have you
gone over to the dark side?  (G)

Chuck, looks like Dave answered your question, how is the observatory going?

Jim

Only partially on the dark side.

----- Original Message ----- 
From: <Aplanatic@aol.com>
To: <astro-photo@seds.org>
Sent: Wednesday, February 25, 2004 3:34 PM
Subject: Re: [APML] Measuring Sky Background With an ST-4


> Hello Jim, Chuck and Geoff.
>
> Geoff found the link (thanks), see below.
>
> Chuck writes:
>
> >Yes I remember it but I don't remember the procedure. It's in the
> >archives somewhere but I know things can sometimes be hard to find.
> >Dave Rowe was the author but I remember him stating at some later date
> >that he didn't think it was as good of a method as he originally
> >thought. Where is Dave these days?
>
> The method works fine, I think, and I still use it from time to time to
> evaluate the darkness of a site.  As long as the same camera is used to
make the
> evaluation, relative results can be compared to each other with reasonable
> accuracy.
>
> The problem occurs when different cameras are used, or absolute accuracy
is
> desired.  Over the years I've had the opportunity to measure a few ST-4's
> side-by-side with my own and have found that they differ by as much as
0.75
> magnitude.  Unfortunately, this limits the usefulness of the test to
"pretty rough,"
> unless a calibration is performed with each individual camera.
>
> I made such a calibration with my own ST-4 under several different sky
> conditions, at several different locations.  This allowed me to calibrate
the ST-4
> to within about 0.25 magnitudes, which I consider to be quite good for
such a
> simple method.  To make the calibration, the local sky background must be
> measured by stellar photometry, a science that is both interesting and
involved in
> its own right.
>
> Dave Rowe
>
> > Jim writes:
> >  > Could not find this in the archives so I thought I would see if some
of
> > the
> >  > long time members remember this.  A thread was done some time ago
> > regarding
> >  > measuring sky background with an ST-4.  Does anyone remember this and
> does
> >  > the information still exist somewhere?
> >
> >   Hey Jim...
> >
> >       Try this link:
> >           http://astro.umsystem.edu/apml/ARCHIVES/JAN01/msg01405.html
> >
> >   Best...
> >
> >  --
> >   Geoff Powers
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