Source locations can be specified using a cursor or by text file. The user is allowed to restrain the extent to which each minimisation iteration is allowed to modify the location, breadth or position angle of the sources. This is essential when the package is used with overlapping sources.
Input text files must contain the x and y coordinates of the source in the Current co-ordinates of the NDF, and may in addition contain estimates for the position angle, Sa, Sb (std deviation of the Gaussian functions in 2 directions - major axis then minor) and the peak value.
Output image options are for the generation of the complete whole image model or an image containing the residuals in the regions surrounding the sources.
There are two separate fitting algorithms within GAUFIT, a non-linear least-squares routine (selectable with parameter LSQFIT=true) or the original parameter-search routine. Some of the parameters below have slightly different behaviour in the two modes, or are only available in one mode or the other. These are indicated by prefacing the variant descriptions with either [PS:] for parameter-search mode (lsqfit=false) or [LSQ:] for least-squares (lsqfit=true)
GAUFIT IN INFILE OUT MODE MODEL IMGDEV
MODTYPE COLOUR ANGCON ANGOFF FWHM PSIZE
BACK SIGMA NSIGMA
LSQFIT=true CALCSD MAXITER
Will read source coordinates from the text file coords.dat. The image on which these appear is image, the output image containing the model for each pixel will be imodel. The coordinates provided by the file are in the Current coordinate system of the WCS component of the NDF image.
ESP --- Extended Surface Photometry