Introduction to IRAF, TABLES, and STSDAS

About STSDAS and TABLES...

With the release of Version 1.3, STSDAS has undergone a major restructuring (see the diagram on p. 25). The TABLES package, which used to be a subset of the utilities in STSDAS, is now completely separate. That is, the STSDAS facilities for FITS I/O, table manipulation, and certain graphics tasks are actually provided through the TABLES package. In this sense, STSDAS is layered both upon IRAF and TABLES, and both must be installed before STSDAS is installed. Throughout the rest of this guide we will describe features of STSDAS which apply equally well to TABLES, though the latter may not be named explicitly. But for those sites that do not install STSDAS, descriptions of utilities found only in TABLES are concentrated at the beginning of Chapter 4 on page 59.

Users who are familiar with IRAF will find that TABLES and STSDAS tasks look similar. Standard IRAF command language functions (i.e., the parameter editor, input/output redirection, file name templates, graphics cursor, etc.) work the same with STSDAS tasks as they do with IRAF tasks. In this sense, STSDAS is simply a project-specific extension of the IRAF system.

IRAF and STSDAS work together as complementary packages with minimal overlap. As a general rule, STSDAS does not duplicate software written by NOAO because the NOAO software can be used within STSDAS for analyzing HST data. Similarly, NOAO observers can use STSDAS software that is not available in the standard IRAF distribution, such as the TABLES utilities, or Fourier analysis. The STSDAS software development group at STScI works in cooperation with the IRAF software development group at NOAO to coordinate software development projects.

STSDAS and IRAF have different native image formats, but because all applications programs access image data through an IRAF system interface, data in either format can be both read and written by applications from either NOAO or STScI. There are some important differences, however, and STSDAS users should see the chapter on data formats beginning on page 37 for more details. As a rule, if you are working primarily with STSDAS applications, keep your data in the STSDAS format. Similarly, if you have Kitt Peak (or Cerro Tololo) data and are using primarily NOAO applications, you should keep your data in the IRAF format. The task imcopy in the IRAF images package can be used to copy data from one format to the other.

IRAF supports a third data format--called Quick Position Oriented Event, or QPOE--for X-ray data, but STSDAS users are not likely to need this format. If you are interested in QPOE format, read the user documentation for the Post-Reduction Off-line Software (PROS) package from the Smithsonian Astrophysical Observatory.

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