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Great attention should be paid to proper settings of the low and high
cuts. They were previously entered as a parameter of the NORMALIZE/IMA command. Now only the original frame is used and it is
not truncated by the applied cuts. The program needs proper values of
cuts in order to avoid using incorrect data. In order to find
acceptable values of cuts one has to redisplay an image several times
with varying values of display cuts. One can, in this way, fix low cut
as a level just below all the good data with only bad pixels having
smaller values. High cut should be placed below the saturation level.
The data may be distorted even at some distance from the saturation
level and the program tries to take this into account. Therefore, in a
case where none of the frame stars are saturated the high cut can take
any value, that is to say, at least twice as large as the highest
pixel value for any stellar object.
As the frames need not be normalised, low and high cuts should be entered
in the same units as pixel data.
Next: Setting the Keywords used
Up: Procedures to Follow
Previous: Preparing Data Frames
Petra Nass
1999-06-15