[vsnet-alert 6017] Re: Possible Nova in Sco

[aah@nofs.navy.mil]

Gianluca Masi wrote:
>Accurate astrometry:
>RA: 17h 57m 06.73s; Decl: -32d 23' 05.6'' (J2000.0).
>Mean residuals: 0.25". Eight reference stars from USNO A2.0.
which "Eight" reference stars did you use? :-)
Seriously, with this crowded field, I could easily imagine picking
8 stars which show low residuals but were all systematically off.
Much better is to use UCAC1 in this region; if your software
does not support UCAC or have access to Vizier, you might
try downloading the USNO-A formatted version of UCAC (sans proper
motion) to be found at
http://ftp.nofs.navy.mil/pub/outgoing/aah/ucac1
as a temporary stopgap.
Arne

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