A common problem with astronomical images is that a few pixels at the centre of a bright star or
galaxy will dominate the dynamic range of the image. If the range of intensities displayed is simply
set from the dynamic range the faint details close to the sky background will not be visible. Script
scaledisp.csh addresses this problem and determines a range of intensities to be plotted which are
closer to the background.
histpeak in ESP to determine the sky background level and a
measure of its variation. The measure used is the mean absolute deviation,
is more robust than the more familiar standard deviation (because it is less sensitive to
outlying values). It is also usually smaller. The image is plotted using KAPPA application
saodisp.csh is similar to
scaledisp.csh, but uses the image display program SAOIMAGE (see
The input for either script consists of the name of the image to be displayed and the minimum and maximum intensities to be displayed. The minimum intensity is specified as the number of below the sky background and the maximum as the number of above the sky background.
ngc2336_r_2.sdf is displayed. The minimum intensity is
below the sky background level and the maximum intensity is