[vsnet-chat 2719] Re: Supernova Magnitude Observations

[Hitoshi YAMAOKA <yamaoka@rc.kyushu-u.ac.jp>]

>     Yamaoka-san asks about the comparison between the various
>"large" star catalogues for astrometry.  

Thank you, Prof. Skiff.  I guess from your comment that USNO_A2.0
is accurate enough when we cannot use Tycho-2.  

If we assume the typical field of view is 10" square, avaraged number
of stars of each catalog in this FOV is:

          whole stars  # in FOV
Tycho-2   2.5 million     1.6
GSC-ACT    25 million    16
USNO_A2.0 526 million   330

Of course, we expect the smaller number for the field far from the
Galactic plain.  Is there any advantage to use GSC v1.2 or ACT in SN
astrometry than USNO-A2.0? 

Sincerely Yours,
Hitoshi Yamaoka, Kyushu Univ., Japan
yamaoka@rc.kyushu-u.ac.jp

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