[vsnet-chat 2123] USNO-A2.0 offsets for Tago nova field

[bas@lowell.Lowell.Edu (Brian Skiff)]

     I had a look at the offsets of USNO-A2.0 magnitudes versus standard R
and B.  The calibration dataset includes Arne Henden's V1315 Aql data, data
for the open cluster Berkeley 82, the two relevant GSPC sequences, and a few
others.  For the two overlapping POSS-I plates, the offset of USNO-A2.0 'mb'
from standard B is close to zero, and in field 513 (east of the nova), the
R offset is also essentially zero.  The field immediately west of the nova
has an offset of 0.4 mag. for R (USNO-A too bright).
     For the moment, of course, one can use Tycho V and B-V, as long as the
errors reported in the Tycho catalogue are < 0.05 mag. for each.

\Brian

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