It is possible to get information on what was used in an SXT table by
using one of these routines. GTAB_COMM returns information on the
common table, GTAB_ENTRY returns information on the entry tables,
and GTAB_ROI returns information on the ROI location and image
shape tables. Some sample calls:
IDL> print, gtab_comm(index)
IDL> print, gtab_comm('15-nov-91')