Software available

The principal Starlink software for reducing CCD images is CCDPACK (see SUN/139[10]). It provides extensive specialised facilities for reducing CCD data. A considerable advantage of CCDPACK is that it is optionally able to estimate and propagate an error estimate for each individual pixel in the CCD frames through the data reduction process. CCDPACK should be used in conjunction with the KAPPA package (see SUN/95[6]), which provides general image display, examination and processing facilities. KAPPA and CCDPACK are completely and seamlessly inter-operable and, indeed, intended to be used together. It is possible to make a reasonable attempt at reducing CCD data using KAPPA alone, though it is less convenient and gives less good results than CCDPACK.

The image processing and spectroscopy package Figaro (see SUN/86[27]) includes some facilities for reducing CCD data, though these are less comprehensive than CCDPACK. Again, Figaro is inter-operable with KAPPA and CCDPACK. In addition to CCDPACK, KAPPA and Figaro there are various other Starlink packages which are relevant to some aspects of CCD data reduction and CCD photometry. The various packages available, their uses and their inter-relations, are conveniently summarised in the `Road-Map for CCD Photometry'[8] which has appeared in the Starlink Bulletin.

The IRAF software environment includes the powerful and extensive package CCDRED for reducing CCD data. The use of IRAF on Starlink systems is described in SG/12[22]. CCDRED is fully documented in:

• User's Guide to the CCDRED Package by F. Valdes[28],

• The IRAF CCD Reduction Package - CCDRED by F. Valdes[29].

Additional useful material may be found in:

• A User's Guide to CCD Reductions with IRAF by P. Massey[18],

• Rectifying and Registering Images Using IRAF by L.A. Wells[35],

• Cleaning Images of Bad Pixels and Cosmic Rays Using IRAF by L.A.Wells and D.J. Bell[36].

The early stages of reducing spectra recorded with CCD detectors are similar to those for direct images, though the later stages differ. There is a thorough and accessible introduction to reducing spectroscopic data in the cookbook SC/7: Simple Spectroscopy Reductions[3].