The program was unable to obtain a satisfactory estimate of the position of the 'sky' in the region above the object.
The algorithm for determining the sky extent uses the median intensity across the profile, and the relative peak intensity. The relative peak intensity is multiplied by a the value of the parameter TUNE_SKYHILIM and compared with 1.05 times the median intensity. The lower of the two values is used as a threshold. When the intensity falls below this threshold, the program denotes the pixels from the current pixel to the edge of the dekker as 'sky'.
TUNE_SKYHILIM may be varied to adjust the threshold. It is also possible to manually adjust the status of each pixel in the profile by setting PFL_INTERACT=Y.
Martin Clayton