IRAF tips

---

If you have never set up IRAF on your linux account, do the following:

• in your home directory, set up an iraf subdirectory: mkdir iraf
• cd into that directory, and type mkiraf. when it asks you what kind of terminal you will be using, say xgterm.
• it will create a file called login.cl. Edit this file in the following ways:
• Change the line that reads #set stdimage = imt800 to read set stdimage = imt8192 (i.e., uncomment and change value)
• Change the line that reads #set imtype="imh" to read set imtype = "fits" (i.e., uncomment and change value)

To start iraf:

• start an xgterm window by typing xgterm -sb &
• in the xgterm window, cd to your iraf directory and type ecl which will start IRAF
• from now on, all IRAF commands should be executed from that xgterm window
• in the xgterm window, cd to the directory that holds your data.
• start ds9 by typing !ds9 &
• you should be good to go now

Miscellaneous tips, as I think of them:

• when using imexamine, remember that the ds9 window needs to be selected/active. if one of the other windows is active, imexamine won't pay attention to your keystrokes even if your cursor is in the ds9 window. (I highly recommend setting up your window manager so that you activate windows by simply moving the cursor into them, rather than the awful default of having to click a window to make it active.)
• you will frequently need to load "packages" to run certain commands. For example, the daofind and qphot commands are part of the noao.digiphot.apphot package. To load this package you would type (in IRAF) noao, then digiphot, then apphot. now you can run daofind and qphot. so if a command doesn't run, make sure you've loaded the package that contains it (which is usually noted at the top of the IRAF help page for that command).
  
• to edit the parameters a command uses, type epar <command> which will let you edit the parameters. do a :wq to save the commands and get back to IRAF.
  
• sometimes commands will have both parameters and subparameters. For example, if you epar apphot, you will see parameters called datapar and findpar. these are actually subparameters. if you go to those parameters and type :e you will get into a new subparameter set. edit those subparameters, then do a :wq to get back to the main parameters, and another :wq to get back to IRAF.
• If you have a file where the first two lines are x,y image coordinates, you can overplot those positions in ds9 by going to Region -> Load Region, clicking All, and then choosing the file. When the load window pops up, tell it that the file format is xy and that the coordinate system is image. (if you had a file of ra & dec, you could tell it the coordinate system is wcs....)
• In any command that wants to know certain keywords from the image header, exposure time is EXPTIME, airmass is AIRMASS, and obstime is DATE-OBS. If you set these this way, you'll be happier. You can always see what's in the image header by loading the image into ds9 (don't display it through IRAF) and choosing File->Display Fits Header.