[vsnet-chat 3558] Re: txcyg

[Brian Skiff <bas@lowell.edu>]

     Since you have a fairly wide field-of-view, it would be best to use
several comparison stars, not just one.  This will allow you to assess
the internal errors in your data and also to guard against one or more
of the comparison stars being variable.  The star you have chosen, which is
BD+41 3954, is quit red (B-V=1.7), so is either reddened or of fairly late
spectral type (K5 given by SIMBAD), so could be slightly variable over long  
timescales.  I would avoid that one.  Within 20' radius are at least four
other more stuiable stars:

BD+42 3937         |21 01 00.915 +42 46 31.37|A0      | 9.78  9.44
BD+41 3952         |20 58 49.950 +42 28 54.59|K0      |11.17 10.11
BD+42 3926         |20 58 45.432 +42 42 17.86|G0V     |10.48  9.93
BD+41 3950         |20 58 31.032 +42 27 32.51|A2      | 9.64  9.44

...where these entries are simply cribbed from a SIMBAD search output.  The
positions are equinox 2000, and the two columns of magnitudes on the right
are B and V respectively.  The V magnitude of BD+41 3954 is 9.02 (the
GSC magnitude is too bright because it is for a redder color system than
standard V).
     I think using a short-focus lens with a CCD is a great way to star
doing variable-star photometry.  It will be better if you can begin to use
a filter at some point in order to place your data ore closely on the
standard system, either V or R.

\Brian

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