Hi John,Hi Roger. You have produced some interesting data.
Were you using NormalizeScaleGradient 1.1 ? The new version calculates the weights more accurately. Thanks to Adam Block for spotting the error in version 1.0
Image weights should depend on the exposure time, the amount of light pollution, and how much light was absorbed by the atmosphere / cloud.
If the dominant problem is light pollution, I would expect a strong correlation with the image median level. On the other hand, if the dominant problem was absorption, the correlation with the median would be low. There should be a strong linear correlation between exposure time and NWEIGHT (provided the conditions stay the same).
Well you and Adam got me motivated to use this script, and I used it early, before it was a PI release.
My NSG scrip run of 100 images was using Rev 0.7 or 0.8. It took over an hour to run. Capturing data (from PI) and putting it into a spreadsheet was a several evening effort. I don't want to do it again just for additional improvement in analysis. I think the results are good to demonstrate the correlations I posted.
I did get a strong correlation with Median, and with Stars Detected, and my main issue was light pollution.