# IRAF Tutorial

How do I view Individual Spectrum Files in IRAF?

The IRAF package has been traditionally used in astronomy for various data analysis tasks. For SDSS data, the splot task has been used to view individual spectrum files. However, splot only understands spectrum files formatted in a specific way. In SDSS DR7 and prior, files were formatted in a manner consistent with splot. If you retrieve these files from DR7, you should have no problem viewing them in IRAF.

Because the structure of spSpec is very constrained, and because the pipeline that originally produced them is no longer used, starting in DR9 we have a new type of individual spectrum file, called a spec file. In a spec file, wavelength, flux, and other data are stored in a FITS binary table. We have a detailed data model for spec files. These files contain quite a bit more data than the old spSpec files.

To extract and plot spectra from spec files in IRAF, we recommend installing the STSDAS tables package. Hodge (1996) shows how to extract and plot data from a FITS binary table, using the tables package. Here is a direct link to the article.