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Administrator
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Hi,
Regarding your questions:
"I just need a clarification on the bias subtraction: if “Bias Subtraction” option is “Enable” during master Dark (or master Flat) creation, using the “Buid” option, the raw Dark (respectively raw Flat) will be Bias subtracted before being average (or median) combined?"
-> yes, that is correct
"Therefore, considering “Dark Subtraction”, what is the difference with the “deBias” option?"
->even though bias subtraction is enabled and is used internally as a bias subtracted dark (if bias subtraction is enabled), a newly created master dark will not be saved with the bias subtracted unless the "deBias" option is enabled. The newly created master dark can be saved either with or without the bias being subtracted (by setting the deBias option), but the deBias option should be set the same way when using a saved master dark as it was set when the master dark was created and saved. This option is mainly for compatibility with master calibration files produced by 3rd party programs. For calibration files created using AIJ, the setting should not affect the outcome, as long as it is always left in the same mode. If the deBias mode is off when creating a master dark, the master dark is saved without being bias subtracted, but is then bias subtracted when it is reloaded and used in DP, as long as deBias is disabled when it is loaded. If the deBias mode is enabled when creating a master dark, the master dark is saved after being bias subtracted, but is then *not* bias subtracted when it is reloaded and used in DP, as long as deBias is enabled when it is loaded.
The main reason for the separate bias and dark subtraction is to facilitate dark current scaling when the darks do not match the exposure time of the science image. If the exposure times are the same, there is not much use in handling the bias subtraction separate from the dark subtraction.
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