[vsnet-chat 3908] Astrometry of cataclysmic variables

[Gianluca Masi <gianmasi@fr.flashnet.it>]

Dear Colleagues,
after the case of RZ Leo, I've trying SIMBAD on targets I imaged, getting astrometry.


Among them, I've found that also KZ Gem has a quite large error. SIMBAD says:

R.A:06 52 58  Decl.:+16 40.3 (J2000.0)

while I measured (see [vsnet-alert 4032]), on an image kindly provoded by T. Vanmunster,

R.A.:06 53 02.47  Decl.: :+16 39 59.2 (J2000.0); 
8 USNO A2.0 reference stars; mean residuals: 0.2" 



As for RX J0459.7+1926, SIMBAD says

R.A.:04 59 43.1  Decl.:+19 26 35 (J2000.0)

while me and A. Cassetti, during the first detected superoutburst of this star have
founded (see [vsnet-obs 26179])

R.A.:04h59m44.05s  Delta: +19d26'23.3"  (J2000.0);
7 USNO A2.0 reference stars; mean residuals:0.15"



Finally, for AW Sge, SIMBAD says

R.A.: 19 58 37 Decl.: +16 41.3 (J2000.0)

while I measured during the 2000 superoutburst (see [vsnet-campaign 374]):

R.A.= 19h 58m 37.11s; Delta:+16d 41' 28.8" (J2000.0)
7 USNO A2.0 reference stars; mean residuals:0.3"


All these stars are in quite dense star fields and the positions given in SIMBAD can be
source of confusion.

As already said by Arne Henden and Taichi Kato, it is clear that in the past astrometry of
this kind of objects had not the same consideration as today; so, maybe that other CVs
(and other kind of variables, of course) are actually catalogued with not accutare
astrometry. When a good reference chart is available this can be a  little problem, but in
different cases one can be definitely confused.

So I would like to suggest to observes, especially when they are doing time-series
photometry of targets in outburst, to perform astrometry as well.

Kind regards,
Gianluca


-- 
***********************************************************************
* Gianluca Masi                           "Two things fill the soul   *
* Via Madonna de Loco, 47               with awe and reverence [...]: *
* 03023 Ceccano (FR)                     the starry sky above me and  *
* ITALY                                    the moral law within me"   *
* e-mail: gianmasi@fr.flashnet.it                                     *
* web:  http://vsnet.eurolink.it/comets/                  I. Kant       *
* Minor Planet Center Obs. Code: 470 - Ceccano                        *
* Center for Backyard Astrophysics - Italy                            *
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* CCD-astrometry-photometry@egroup mailing-list moderator             *
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