CORRECT: Correct Photometry for Extinction and/or Transformations

CORRECT applies photometric corrections to raw data to account for extinction and/or transformation terms. It can act either on a number of types of stellar photometry files (e.g. standard DAOPHOT files or files that come from the MAGAVER| command), or internally on the surface brightnesses and magnitudes in the internal PROFILE common block. Besides the input data, the routine reads a file with the extinction and transformation coefficients. This file may be created using the FITSTAR command, or for more simple cases in which you wish to dictate the extinction and/or transformation coefficients, it may be created by the user by hand. See the FITSTAR help file for a description of this transformation (.trn) file.

When you run CORRECT, the routine will prompt for a transformation file name, unless you supply one with the TRN=trnfile keyword. It will list the various lines in this file and ask you which transformation you wish to use; alternatively, you can pre-specify the line to use with the LINE= keyword. If you have observations in more than one color (in MAGAVER files), you will be asked which magnitude you wish to correct, and which colors to use for the color terms (or you can specify these with the COLCOL= keyword). If you have observations in only one color, you will be asked if you wish to enter a standard color to use in the transformation equations, unless you have pre-specified this number using the COLOR= keyword. The routine will then proceed to apply the transformation equation(s).

If you are correct stellar magnitudes, you will be prompted for an input and output file name. If you are using the PROF option, the internal counts in the PROFILE common block will be corrected. The reduced PROFILE counts (or magnitudes) can be seen using the PRINT PROF [MAG] command. With the PROF option, several auxiliary value are computed, namely the concentration index (ratio of radii that include 25 and 75 percent of the light), the total magnitude (extrapolated for an exponential disk if one has been fit using the CPROF command), and the disk-to-total light ration (using the exponential fit if done). These values are loaded into the internal PROFILE FITS header, and also printed out with the PRINT PROF command.

NOTE: For the PROF option, the counts will be corrected for exposure time and the airmass computed. This requires that accurate values for EXPOSURE, RA, DEC, DATE-OBS, and the latitude are available. Since the PROFILE header is originally copied from the image header, these values should be available. If they are not, note that cards can be added and/or removed from the internal PROFILE header using the FITS, UNFIT, or HEDIT command with the PROF keyword instead of a buffer number.