[vsnet-chat 4230] (fwd) Re: Guide 7 data error

[Taichi Kato <tkato>]

(fwd) Re: Guide 7 data error

Date: Tue, 17 Apr 2001 20:18:02 -0500
From: "Bill J. Gray" <pluto@projectpluto.com>
Subject: [vsnet-chat 0] Re: Guide 7 data error

   (I'm not actually on this list,  but John Greaves and Fraser Farrell
were kind enough to copy their messages to me.)
 
   John is correct;  several few bright stars were missing from
Tycho-1 and GSC,  including this one.  (The one about which I've been
asked most frequently is SAO 76188 = PPM 92833 = HD 23608,  a mag 8.67
star not far from Eta Tauri,  in the Pleiades.)  Tycho-2 repairs this
and several other omissions,  which I'm sure will mean simply that
omissions will now be found at about a magnitude fainter level.

   John is also right about the naming convention.  Stars not in GSC
were given an "area" identifier matching their observed RA/dec,  and
the first available number not already in use by GSC.

   Fraser Farrell wrote:

   "...Guide shows a ~10' diameter semicircle of 14th & 15th mag
GSC stars centred on this position. Are these actually a
7th-mag star image which happened to fall on a plate defect?"

   I don't think so.  The DSS image for this area shows nothing of
particular interest (though unfortunately,  we don't have access to the
scan actually used for GSC here.)  There are a slew of faint stars in
the area;  as often happens with GSC,  you can't really tell why those
particular 14/15 mag stars were chosen,  while others of seemingly
similar brightness were dropped.

-- Bill

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