Performing profile fitting analyses

To perform a profile fit a list of the accurate positions of good well separated stars are required. One way to get such a list is too use the KAPPA CENTROID routine to select objects from a displayed image.

   # centroid coout=stars.acc mode=cursor mark

The output file stars.acc is of a format suitable for input to PISAFIT. Running PISAFIT allows the determination of the best fit to the stars.

   # pisafit
   IN - NDF containing input image /@frame/ >
    Analysing whole image
    Estimated background level =   492.2
    Background standard deviation =     7.4
   BACKGROUND - Background (global sky) value /492.2/ >
   POSITIONS - File containing star positions / / > stars.acc
   MINMODE - Minimisation bounds mode /'APM'/ >
   RADIUS - Limiting Radius > 10
    Number of points in curve fit = 28

    May be having problems with the minimisation, check plot.
    RMS of fit                 = 2.0545775E-02
    Gaussian Sigma      (GSIGM)=  2.17
    % Cross Over        (CROSS)= 30
    Mixture Coefficient (COMIX)= 0.087
   AGAIN - Do fit again /TRUE/ > f

The parameters controlling other various options are detailed in the routine description appendix. Usually the default options (as shown) are all that are necessary.

PISAFIT writes the model parameterisations into the application's parameter file. These values are then automatically picked up by any other PISA application which requires them. So for instance running PISAFIND in its profile fitting mode is straight-forward after running PISAFIT.

   # pisafind
   IN - NDF containing input image /@frame/ >
    Analysing whole image
   MINPIX - Minimum pixel size for images (typically 4-16) / / > 4
   METHOD - Intensity analysis ( 0=Isophotal, 1=Total, 2=Profile ) /0/ > 2
   GSIGM - Gaussian sigma (pixels) /2.17146/ >
   CROSS - Crossover point % of peak /30/ >
   COMIX - Mixture coefficient /8.7035753E-02/ >
   UPLIM - Upper intensity limit to use in analysis (saturation) /32767/ >
   IFULL - Do you want full surface modelling /FALSE/ >
    Estimated background level =   492.2
    Background standard deviation =     7.4
   BACKGROUND - Background (global sky) value /492.17/ >
   THRESH - Threshold for analysis (data units) /20/ >

    Total number of positive images = 119
    The results have been written to pisafind.dat
        and pisasize.dat