How to compute an offset master image under
ISIS
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The offset (or bias) is a spurious signal produced by an electronic shift of
the camera. We observe that signal in an image taken with
an exposure time of almost zero and in darkness. The offset signal is present in
all images Offset must be subtracted in the process stage for extracting clean signal of the observed star. Right, the Audela software acquisition panel during offset sequence acquistion. |
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From "Master images" tab, we
compute an offset image from individual o-1 o-2, ..., o-15. The result is offset.fit image in the
working directory. Tip: make a habit of adopting the same name for yourcalibration images calibration. A generic name such as "o-xxx"is easy to type during acquisition. Do not complicate your life. A name like "offset.fit" is also explicit. Above all, do you make a strict protocol and did not deviate! |
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