Re: Question about Gemini guide stars...[Fwd: Gemini preferences]

From: Robert A. Knop Jr. (robert.a.knop@vanderbilt.edu)
Date: Wed Nov 06 2002 - 15:26:51 PST

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On Wed, Nov 06, 2002 at 03:13:20PM -0800, Alex Conley wrote:
> that the same stars give different magnitudes in the different finding
> charts. This is why you can't trust APM/USNO magnitudes very well on
> really deep images like these. Doh!

Plus the USNO catalog is in the R band, and these are i' images.
Typically not very many stars will be used in the zeropoint calculation,
so the random scatter of the colors can be important.

Trust the finding chart coordinates, but the sntrak magintudes.

-Rob

-- 
--Prof. Robert Knop
  Department of Physics & Astronomy, Vanderbilt University
  robert.a.knop@vanderbilt.edu

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