[vsnet-chat 734] Re: USNO-A

[Taichi Kato <tkato>]

Dear Dr. Henden,

   Thank you very much for your suggestion.  I will use, for consistency
with the IAUC designation of existing variables, "USNO" + sequence_number
format for USNO A1.0 objects.  I hope, at the time of the release of USNO
A2.0, the USNO catalog team could show some kind of recommendation of
nomenclature of USNO objects, to all potential users, in order to avoid
possible inconsistencies arising from the mixed usage of different versions
of catalogs, and different format of nomenclature.  (Well, there is already
a problem for USNO SA1.0 users, since the running number is different from
that of USNO A1.0).  I will then follow the recommendation by revising my
extraction and display program.

   Can I have one more question on the photometric system of the USNO
catalogue?  We have had much concern in the potentiality of the USNO catalog
for preliminary comparison for deep visual variable star and comet observing.
I have derived an experimental equation of V = r + 0.375(b-r), where b and r
represent blue and red magnitudes in USNO, and have used this to create
some of preliminary charts in this forum (some of them have been subsequently
replaced by CCD-based V measurements).  Though it seems to me this kind of
linear color transformation seems to be enough for limited range of colors
(excluding blue stars strongly emitting the UV light and extremely red stars)
and for the visual accuracy, is there any such kind of transformation which
can be used as an international standard?  Some of our readers also request
a similar equation for the R (probably Rc) band.

Regards,
Taichi Kato

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