Good finding charts and accurate positions of targets and corresponding guide stars (autoguiding facilities are available with most instruments) invariably result in more efficient and trouble-free observing. A range of facilities are available at the RGO Cambridge to assist visiting astronomers in preparing for their observations. Paper and glass copies of the first epoch Palomar Sky Survey and film copies of the ESO and PPARC Schmidt surveys of the southern sky and the second epoch Palomar sky survey are located in a chart room which also houses Starlink terminals, Polaroid cameras, light tables and an extensive set of star catalogues and celestial atlases. Programs are available to produce overlays to aid target identification on the sky survey plates or give offsets and guide star information for individual telescopes and instruments. A Coradograph measuring machine with interfaced microcomputer is available to measure accurate positions (typically to better than 1 arcsec) of objects of interest relative to a grid of reference stars suggested by the programs. Glass and film copies of the sky survey plates are used for this purpose.
A copy of the NASA/STSCI Digitised Sky Survey on CD-Rom is available, together with software to access it on a Sparcstation.
Lastly, the important APM facility (operated by the RGO) has an
accurate plate-scanning machine and can on request produce finding
charts and measure positions off Sky Survey plates. The APM stored
Catalogues contain stellar and non-stellar objects, with for example
stellar magnitude limits of about 
& R=20
for the North (from Palomar O & E
plates) and 
& R=21 for the South (from UK Schmidt plates).
Typical internal accuracy is 0.1--0.25arcsec but about
0.5arcsec in the external reference frame. The Catalogues can be
accessed over the INTERNET network.
Fuller details are in Spectrum, 2, p14 (1994).