Hybrid cross/self-correlation

The SELFCW application performs a calculation that is essentially the same as that of CORR but where the raw pixel values used are replaced by RMS (sign maintained) values derived from a list of diameterically opposed equidistant pixel pairs found within the mask region. It thus represents a mixture of the symmetry based SELFC and the template cross-correlation CORR. This hybrid self/cross-correlation appears to produce fewer spurious objects than the two previous methods and appears to be less sensitive to noise. It is again normalised to the 0-1 range and significance testing may be performed as before.

The application can be used with the following syntax:

% selfcw in=p2 out=scp2 scale=15. psize=1. back=1000. useall=true

Using this example a hybrid correlation image is generated which has been optimised to detect galaxies of 15 arc second scale length on the image p2. No pixels have been excluded from the calculations. Other examples of the syntax required to use this application are given Appendix B.1.