The bin size used for the histogram defaults to 1 adu unless overridden by the bin option on the command line. A warning message is printed if the given bin size leads to too many bins and possible truncation of the histogram at the high end.
min and max specify the lowest and highest data value used in the histogram; they default to zero and the maximum possible data value.
If pix=n is specified, only every n'th pixel is used in computations. This can speed up execution times on large images.
The histogram operation can be limited to a box or circle via the box or circle options respectively.
Unless quiet is specified, a number of statistics such as the median, the mean, and the histogram maximum are printed out on the screen. These statistics are computed with all pixel values, even those outside the range specified by min and max.
hist orion box=3
Computes the histogram of the image file orion.fts inside box 3, using the default binsize of 1. The resulting histogram data are written into a file called orion.his.
hist crab min=sky max=5000 bin=2
Computes a histogram of binsize 2 for all pixels with values between the SKY value (which must have been previously calculated) and 5000, writing the results to the file crab.his.