rgsangles adds the dispersion and cross-dispersion channel numbers for each event to the EVENTS table. This involves correcting the event coordinates for aspect drift, which is done with respect to the primary source position specified in the SRCLIST table. The corrected floating-point coordinates are also added to each event, and the computed constants of the correction formula are added to each frame for the later construction of the exposure maps. The “binning” of the floating-point coordinates into discrete channel numbers is controlled by the task parameters, and these channel definitions are documented as attributes of the BETA_CHANNEL and XDSP_CHANNEL columns of the EVENTS table.
