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Thanks Bert,
Those images were great.
I have attached a zipped Excel file with the results of my analysis.
This is what I did.
I randomly sampled 10, 99x99 sections of each image and recorded the mean and standard deviation. The signal to noise ratio is calculated as the Mean/SD (Berry & Burnell, 2000, page181).
I also applied Noiseware professional to the ICNR OFF image and examined the same samples from the image.
It can be seen from the results that the ICNR produces a higher signal to noise ratio than the calibrated image in all samples. This confirms our earlier observations.
Interestingly, when the calibrated frames have Noiseware applied with the default settings, the signal to noise ratio improves almost to the same level as the ICNR.
Although not conclusive, these results strengthen my contention that ICNR is doing something else other than simple dark frame subtraction. As noise reduction can create artifacts, I would lean towards not using the In Camera variety.
So I guess that it still somes down to your own preference. Certainly, using ICNR will speed processing by removing the need to do dark and bias calibration, and post processing noise reduction would probably not be required either. The trade off then is still the same. Time at the scope or time in processing.
Please let me know if I have done something stupid or that my thinking is wrong.
Thank you again for posting these images and sparking an interesting discussion.
Of course I am keen to hear others opinions as well.
Cheers
(ref: Berry R & Burnell J, The Handbook of Astronomical Image Processing, William Bell Inc, 2000)
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