The cross-self-correlated image may be used to find faint diffuse objects for a given scale length.
The circular exponential profile template used is of a size that optimises the search for galaxies of the scale length requested by the user.
To reduce the influence of bright objects or cosmic rays; the user may elect to employ a cut out pixel count value where any pixel found to be above that value is ignored. The cutout value is determined by the user inputting a global background count value (available via HISTPEAK), the background count standard deviation and the number of standard deviations above sky level at which the cutout should occur.
The user is required to enter a value for the scale length of of the object(s) of interest and also the image pixel size.
The method assumes some sort of symmetry is present in the objects detected but appears to work well on a wide range of image types.
A border is present in the output image which is of the same width as the radius of the template. All pixels within this border are assigned the value bad.
The correlation is optimised by making the template size 1.8x that of the galaxy scale length required. This factor was determined from simulations by Phillipps and Davies at Cardiff.
All pixels with a count value greater than 444.12.x4. are excluded from the correlation calculations.
To establish the statistical significance of a detection, this application should be used in conjunction with MIXUP to allow noise equivalent images to be generated and correlated thereby establishing a 3 sigma limit.
ESP --- Extended Surface Photometry