Read this if you are familiar with the sources in your field of view and you want to build your own catalog for the Imaging step.
As already discussed in Section 8.3.1, during the imaging step (IMA) it can be very useful to use your own input catalog. The easiest way to build it is to modify the general catalog with the help of the fcopy program of FTOOLS. For example, if you want to create a catalog (usrcat.fits) with only three sources, Crab, 3C111, and XPer do the following:
cd $REP_BASE_PROD fcopy "$ISDC_REF_CAT[NAME == 'Crab'|| NAME == '3C 111'|| NAME == 'X Per']" usrcat.fits chmod -w usrcat.fits
If you want to add a new source, not specified in the general reference catalog, add a line to usrcat.fits with the help of the fv tool, and fill in the Source_ID, NAME, RA_OBJ and DEC_OBJ columns. As Source_ID you can choose whatever you like provided that this identifier is unique.
NOTE: usrcat.fits keeps the same format of the general reference catalog from which it was built, i.e. it has the extension of the type "GNRL-REFR-CAT". This is the correct extension to be used as input for the Imaging step. In Section 7.2, you have been shown how to build a catalog for the lightcurve (LCR) and spectral (SPE) step. In that case the catalog, you obtained, specat.fits, was of the type of "ISGR-SRCL-RES" which is the correct format for the LCR and SPE steps. The two formats cannot be switched, meaning that you cannot use a "GNRL-REFR-CAT" type catalog for SPE and LCR or an "ISGR-SRCL-RES" one for IMA.