The APM Sky Catalogues: Overview
Over the last few years we have used the APM facility to measure the
first epoch Palomar O and E sky survey plates, with the aim of constructing
a readily accessible Northern sky optical catalogue (see Gemini No. 37
and Spectrum No. 2 for more details). We now have available
an on-line catalogue which includes fields to within 
of the
Galactic Plane. Most of the on-line catalogue covers the North Galactic cap,
centred at 
, whilst the South Galactic cap appears
in two regions located at around 
and 
.
The catalogue is based on digitised scans of both the blue O plates and red
E plates covering some 15000 square degrees of sky and with parameters
for well over 150 million images recorded. Both B1950 and J2000 astrometry
is available and was calibrated by using the appropriate 200+ PPM astrometric
standards per Palomar field. More details of the accuracy of
astrometry derived from Schmidt plates are given in an article published in
the Working Group on Wide Field Imaging - Newsletter 5 p25-30.
A similar catalogue is in the process of being constructed for the Southern
hemisphere based on UKST sky survey IIIaJ and IIIaF plates. This is being
put on-line in a similar manner to the Palomar survey as it becomes
available. The main limitation in construction of the Southern catalogue
is the limited number of SES R survey plates in the high latitude fields
south of 
.
Mike Irwin mike@ast.cam.ac.uk