Hi Fred
I agree. A 1 hour exposure and a 5 hour dark is excessive.
I suppose it depends on the amount of noise obsession you suffer from.
If you look at the icnr of the latest DSLR's then if you do a 30 min exposure the icnr will do a 30 min dark. I see that as a minimum.
I do also understand the point of dark frames exceeding the exposure time as the thermal electron generation varies from about .001 electrons/pixel/sec to about 30 electrons/pixel/sec depending on type of sensor and whether its cooled or not.
I think however that when you are shooting very faint DSO's where other noise dominates and buries the signal then you might be forced to go to these extremes.
My approach to this, as i use track and stack with short exposures is , if I shoot 60 second subs then I will do a few 120 to 300 sec darks, combine these darks into a master dark and use the master.
I will investigate this issue futher and post further comments as the rationale and math behind this approach is quite comprehensive.
Regards
Steve
