dsub subtracts a dark frame from many others, overwriting the frames. It scales the dark frame according to the ratio of exposure times, if they can be found. It aborts if the exposure times cannot be found. The dark frame must be bias subtracted and created from a series of frames with identical exposure times.
There are some subtleties with dark subtraction. If the data are bias subtracted and the bias has a significant exposure time, then rather less dark needs subtracting. Thr reverse applies if the dark itself has had a finite length bias subtracted.
dsub flist dark [coerce nccd nwin]
| flist | --- | Frame list |
| dark | --- | Dark frame to subtract |
| coerce | --- | Coerce the frame to be subtracted the input file formats or not. Not always possible: needs binning factors to be correctly related and window start positions to match up correctly. |
| nccd | --- | CCD number if only one to be subtracted, except that 0 means all but then allows a particular window of each CCD to be handled. |
| nwin | --- | Window number if only one to be subtracted. |
See also add, mul, sub, div, uset, cadd, csub, cmul, cdiv, mdiv and msub.
This command is a member of the classes: Arithematic, Programs.
Author: T.R. Marsh
Created: 06 Jan 2006
Revised: 13 Nov 2007