Quote:
Originally Posted by jase
Actually, a question on this data. What caused the FITS masters to have a mean background ADU value of .01? Is this a result of the way PI produces masters or the data being previously stretched?
Put another way, why has the pedestal value been blown away? Post calibration, what were the values of the subs? Were there any subs with a value below zero? A no point should this occur. If it does, you need to back track to find the root cause. This is the reason why all FITS apps add a pedestal value (typically 100 counts) to stop FITS becoming negative.
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Jase,
A pedestal isn't needed after calibration has been done and the data has been converted to 32-bit floating point.
Unfortunately, the FITS spec doesn't specify a standard range for floating point data values. PI uses a range 0..1 Other packages use different values. You can tell PI to use a different range when reading "foreign" FITS files.
Cheers,
Rick.