1 Introduction

THIS IS BETA SOFTWARE. Some features work only partially or unreliably. It does not have all the functionality of a production release. The interface may well change.

Starlink's ASTROM application provides powerful astrometry facilities, for analysing astronomical images; it is, however, rather cumbersome to use. As described in SUN/5, ASTROM can:

• obtain the plate centre and plate scale of a CCD image, by comparing plate positions of objects with those in a reference catalogue, and fitting with both four- and six-component distortion models;
• with enough data, obtain cubic distortion and plate tilt, using seven- to nine-component models;
• if enough information is available, it will do the reductions in observed place, correcting for atmospheric refraction.

• work on a CCD image provided as an NDF, as long as it has at least rough astrometry (plate centre and scale);
• automatically download appropriate reference catalogue information from catalogue servers supported by the SkyCat library;
• insert the astrometric results into the original NDF, as a WCS component;
• alternatively or additionally make the astrometry available as a set of FITS-WCS header cards.