|
Cheers mate :-)
I know it's unusual, but dark subtraction on the narrowband set definitely did reduce the noise in the resulting integration, both visually and measurably.
The stddev was ~1094 (16-bit scale) for the dark-subtracted integration, and ~1216 for the integration without darks and I understand this to be a good measure of noise.
A couple of things of note there is that it also had a measurable difference in the image as well. An identical stretch looked quite different when applied to a small region in the resulting integrations. The median also differed by over 20% (529 with dark vs 420 without). This had the effect of decreasing global contrast, which you can see in the attached crops which were stretched identically.
Dark subtraction is known to increase noise in the integration, thus the reason I was comparing integrations with dark, without dark and without dark but with defect map, but these results aren't what I would expect.
I wonder if this is related to the mismatch in temperature, with the darks being shot at 5c lower than the lights... I would have expected this to increase the noise if anything...
|