--- "Mike Potter" <mike@...> wrote:
> It's a bit more tricky to scale darks for temperature
> differences as the dark current is actually an
> exponential function of temperature.
FYI, older versions of CCDStack had an option for autoscaling time
and temp via linear and exponential OLS fitting. But I eventually
removed the exponential component because I found that the result of
this method usually produced a calibrated image that largely tamed
the hot pixels but the "normal" pixels were not as well fitted as
linear OLS. I find that a linear autoscale method applied to temp-
different frames lets the few hot pixels go crazy but results in a
good fit for the vast majority of pixels. Those hot pixels are then
easily killed via kernel filter ("hot/cold") or stack-rejection (e.g.
sigma).
As a practical matter, temp scaling should rarely if ever be used for
SBIG cameras because they are well regulated and it is very easy to
take same-temp darks. Temp scaling is most useful for unregulated
Cameras, where you do not know the temp &/or the temp varies during
the exp.
Stan
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