[vsnet-chat 2382] sn1999em field photometry

[aah@nofs.navy.mil]

After a cloudless October, we are now in a
zonal flow pattern with Pacific cirrus.  I've
observed the SN 1999em field under non-photometric
conditions, and tied the zero points to Longo & de Vaucouleurs
star GSC 4739-0434 as suggested by Brian Skiff in
vsnet-alert 3641.  I used the following magnitudes:
    V   12.36
    B-V  1.23
    V-R  0.74
    R-I  0.72
where the latter two are crude transformations based
on Landolt stars.  The resultant file can be found at
http://ftp.nofs.navy.mil/pub/outgoing/sequence/sn1999em.dat
While conditions are not forecast to be very favorable,
I will keep this field on my program and if it becomes
photometric over the next few nights, I will update
this file with calibrated values.  In the meantime,
the current version should be good enough for visual
work and will be internally consistent.
Arne

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