SECTOR: Surface Photometry of Star Clusters or Complex Objects

SECTOR measures the brightness distribution of a star cluster or any other extended object by adding up the flux in a set of circular isophotal rings. Errors in brightness in any ring are calculated by dividing the ring into eight angular sectors and intercomparing the individual sector results. The final profile is saved in the MULT block, and can be saved or gotten with the MULT keyword in the SAVE or GET commands, printed in the PRINT command, or plotted with the PLOT command. The object can also be reconstructed with the RENUC command.

The center should be found first with the AUTOCEN or AXES command. The C keyword can be used to override the default center. Isophotes increase linearly from the center at first, and are spaced by the lin entry with the RAD keyword. When a geometric increment given by the geo entry gives a larger spacing, it is used to space the outer isophotes. The radii used are at the radii at which the area of the isophotal rings is evenly divided. Pixels can be excluded from the calculation by setting them to zero.