[vsnet-chat 3894] Re: [CCD-astrometry-photometry] RZ Leo astrometry

[aah@nofs.navy.mil]

Gianluca,
  My measurements of the coordinates of RZ Leo during
quiescence can be found in the Sumner sequence at:
http://ftp.nofs.navy.mil/pub/outgoing/aah/sequence/sumner/rzleo.dat
and are:
11 37 22.27  +01 48 58.7 J2000
which are in agreement with your measures of
11 37 22.27  +01 48 58.9

The master CV catalog of Downes, Webbink and Shara
(PASP 109, 345, 1997, often referred to as DWS in
this business) give
11 37 22.30  +01 48 57.8
again in agreement with the two measures above, considering
that they were using the GSC for their astrometric reference.

The discrepancy with Simbad is that Simbad is using the
coordinates from the first CV catalog (Downes and Shara,
PASP 105, 127, 1993, also known as D&S).  There was a
misidentification in that earlier catalog.  This is a common
problem with CVs that did not have good astrometry when
they were discovered in outburst and which have not been
seen in outburst since.  Downes and Shara have done the
best job they could, but you will find many such
misidentifications on the poorly observed cataclysmics.
The way I've found many of these is by color; deep exposures
are necessary to find CV's at 20th magnitude in B&V, but
it can be done.  Such a technique is not perfect, as many
CVs are very red in quiescence, but it picks out the blue
ones pretty easily.
  However, you should report this coordinate discrepancy
to Simbad to update their database.
Arne

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