Introduction to Reducing HST Data

A.1 Initiating IRAF

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This section explains:

• How to set up your IRAF working environment.
• How to start and logout of IRAF.

We assume that your site has IRAF and STSDAS installed. If not, you should obtain and install the software. See Appendix A.3 for details.

A.1.1 Setting Up IRAF in Unix/Linux

Before running IRAF for the first time you need to:

1. Create an IRAF root directory.
2. Move to that directory and set the necessary environment variables or system logicals and symbols.
3. Run mkiraf to create a login.cl file and a uparm subdirectory.

Users generally name their IRAF home directory iraf (also referred to as your IRAF root directory) and put it in their user home directory (i.e., the default directory that you are in when you log in to the system). The IRAF home directory doesn't need to be in your home directory, nor does it need to be called iraf, but you should not put it on a scratch disk that is periodically erased.

If you call your root IRAF directory "iraf", you can set up IRAF as follows:

The mkiraf command initializes IRAF by creating a login.cl file and a subdirectory called uparm. After typing the mkiraf command, you will see something like the following:

% mkiraf -- creating a new uparm directory Terminal types: gterm=ttysw+graphics,vt640... Enter terminal type:

 

Enter the type of terminal or workstation you will most often use with IRAF. ¹ Generic terminal types that will work for most users are:

• xgterm for sites that have installed X11 IRAF and IRAF v2.10.3 BETA or later.
• xterm for most workstations running under X-Windows.
• vt100 for most terminals.

IRAF for other systems, like Mac OSX, can be obtained from the IRAF web page at: http://iraf.noao.edu

You can change your terminal type at any time by typing (set term=new_type) during an IRAF session. You can also change your default type by editing the appropriate line in your login.cl file.

After you enter your terminal type, you will see the following message before getting your regular prompt:

A new LOGIN.CL file has been created in the current ... You may wish to review and edit this file to change ...

 

The login.cl file is the startup file used by the IRAF command language (CL). It is similar to the .login file used by Unix. Whenever IRAF starts, it looks at the login.cl file. You can edit this file to customize your IRAF environment. In fact, you should look at it to make sure that everything in it is correct. In particular, there is a line starting with set home = that tells IRAF where to find your IRAF home directory. You should verify that this statement does, in fact, point to your IRAF directory. If you will be working with standard IRAF format images you should also insert a line saying set imdir = "HDR$". The imdir setting is ignored when working with GEIS and FITS format images.

The uparm directory will contain your own copies of IRAF task parameters. This directory allows you to customize your IRAF environment by setting certain parameter values as defaults. Once you set up IRAF, you should only have to do it again when you install an updated version of IRAF.

A.1.2 Starting and Stopping an IRAF Session

To start an IRAF session:

1. Move to your IRAF home directory.
2. Type cl.

IRAF starts by displaying several lines of introductory text and then puts a prompt at the bottom of the screen. Figure A.1 is a sample IRAF startup screen.

Figure A.1: IRAF Startup Screen

 

To quit an IRAF session:

Type logout.

¹Users at STScI should consult the STScI Site Guide for IRAF and STSDAS.

	Space Telescope Science Institute http://www.stsci.edu Voice: (410) 338-1082 help@stsci.edu