Recipe primitives

After the steering primitive we come to the recipe-specific scripts that actually perform the recipe. The most likely and easiest things you would change are to add arguments or modify argument values of the primitives in the recipes. For instance, you might wish to change the aperture diameter for the aperture photometry. To alter to a 4-arcsecond aperture, change the APERTURE argument's value of the _APHOT_MAG_ primitive like below.

      _APHOT_MAG_ APERTURE=4

To obtain details of a primitive's arguments, use the oracman or perldoc command. Thus

 % oracman _MAKE_MOSAIC_

will display the documentation for primitive _MAKE_MOSAIC_. Space does not permit inclusion of the documentation of the many primitives in this manual. Most of primitives' source code is stored in $ORAC_DIR/primitives/imaging; the instrument-specific ones are situated within $ORAC_DIR/primitives/<instrument>, where <instrument> is UFTI, UIST, MICHELLE, IRCAM, IRIS2, ISAAC, or INGRID; and there are a few general scripts in $ORAC_DIR/primitives/general.

While the simplest primitives just invoke a Starlink task, and updates just that and are amenable to customisation, some are quite complex especially for the registration. They may invoke other primitives, manipulate parameters and small data files so that the various tasks connect to cope with a variety of circumstances. The most likely change you will want to make is to change the parameter values of a Starlink task. Armed with the reference documentation for the application, say with a findme <application>, it is easy to change values or append further parameters.

Here is an example. Let us suppose you wanted to combine frames to make a self flat, not with the median, since you have heard that a mean trimmed of the most-extreme tenth of the values gives better results. First copy _MAKE_FLAT_FROM_GROUP_ to your primitives directory.

 % cp $ORAC_DIR/primitives/imaging/_MAKE_FLAT_FROM_GROUP_ $ORAC_PRIMITIVE_DIR

Using an editor, find the first line in your copy of _MAKE_FLAT_FROM_GROUP_ commencing $hidden. It should be as follows.

      $hidden = "method=median sigmas=2.0 reset accept";

Change this to

      $hidden = "method=trimmed alpha=0.1 sigmas=2.0 reset accept";

to effect the change of statistic. There is in fact a second line assigning variable $hidden depending on argument CLEAN, and you should make the same alteration there too.

If there is demand, additional arguments could be provided for primitives, to simplify control. Please contact the author if you have suggestions for arguments and new recipes, or need help customising your ORAC-DR scripts.