Running from the IRAF cl

POLPACK is written for the Starlink software environment, but may also be run from the IRAF cl, reading and writing IRAF .imh image files using the `on-the-fly' data-conversion facilities described here.

Assuming that all the required software has been installed in the recommended way and IRAF initialised as usual, the POLPACK may be loaded at the cl prompt by:

cl> polpack

the menu of commands will be displayed as for normal IRAF packages and applications are invoked and help obtained in the normal way. However, the IRAF Cl is not the Starlink software environment, and you will find some differences in the way POLPACK behaves when run from the two environments (other than the obvious ones like the way parameters are prompted for). These include:

• The POLHELP command is not available. Use the IRAF help system instead.

• In transforming data from NDF to IRAF format, some information may be lost. In particular, any VARIANCE component in an NDF will be lost and so variance estimates will not be made by POLPACK. Also, bad pixels within NDFs will be replaced by the value zero when converted to IRAF format.

• Some of the Starlink packages which you may be used to using with POLPACK may not be available under IRAF. For instance, at the moment the CURSA package which can be used to manipulate catalogues of polarization vectors is not available under IRAF.

The experienced IRAF user will also detected some differences between the way POLPACK runs under cl and the way standard IRAF packages run under cl - in the areas of graphics and parameter handling for instance. Some general guidance on running Starlink applications from IRAF cl is given in SUN/217. A description, intended for programmers, of the way Starlink packages are set up for use with IRAF, and some technical detail about how the system works is in SSN/35.