Let us take the hypothetical situation that an observer has an observing program that consists of repeated short exposures on a single field through two filters, each with different exposure times. S/he could spend the next three hours typing observe over and over, each time changing the filter, focus, and exposure time. Or s/he could write a short script that would repeat this sequence, freeing the observer to pay attention to results and enjoy a cup of coffee. How would we go about this?
The sequence that we want to emulate is something like the one shown in Fig. 13. The script we write for doing this in an easy and relatively painless manner is shown in Fig. 14.
This has been a relatively simple example, but perhaps illustrates how a little cleverness can save you an immense amount of work at the telescope. Dave Silva has put together a set of such scripts of varying complexity, intended as simple observing aids, and we list them below:
While it is possible to get yourself into trouble using these scripts, we believe the potential benefits to one's observing program outweigh the potential for loss of time. These examples are meant to be illustrative of what can be done; they have all been demonstrated to work at the 0.9m, and extensions to other applications will doubtless occur to you. You can readily modify these scripts as you wish; understand, though, that their availability comes with the disclaimer that you use these scripts at your own peril.
To use the unmodified version of these scripts, you simply need to type the command as inferred from the above list, i.e., reformat. To modify a script you need only edit it; they are located in a subdirectory of your home directory called scripts, i.e.,
You can also copy one of these scripts to a new file and run it; in that case you will need to define it as an external task:
Note: Because the observe task is patiently waiting you to interrupt it with a keystroke once you begin an exposure, it is no longer possible to run simple lists of commands by doing a cl < scriptname.cl.
Additional information can be gleaned from the help pages for these scripts (i.e., help obslooper) and the README file in the scripts subdirectory. We recommend that one always keep a copy of the An Introductory User's Guide to IRAF Scripts by Anderson and Seaman handy; a copy is located in every dome in the Big White Binder (``KPNO IRAF Documentation")