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Outlier Rejection

White Dwarf Customer
Joined: 2 years ago
Posts: 30
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Yesterday, my stack had very bright satellite/aircraft streaks.  I hadn't selected any outlier rejection, so I wasn't concerned.  I went back and read the verbiage where it suggested that "Adaptive" combined the best of the other rejection programs, Windsor and Sigma.  

I selected it and re-stacked.  Well, the result was for sure an improvement, but not an adequate improvement as the streaks were still very visible.  I thought I would have to find a way to examine each frame and hand delete the bad ones.  This is probably a good idea.

Instead, just to see, I re-stacked again using Sigma.  Sigma worked completely.  So, there appeared to be some warning, do these rejection programs bite my signal data?  Is it in fact a better idea so tediously sift the light frames "by hand"?

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Quasar Admin
Joined: 5 years ago
Posts: 4736

Depends on the data really, if it's reaaaallly bad it might be better to leave out some of those frames. But it requires some experimentation if the automatic settings don't work well, you can lower the value for the kappa-high to get a more aggressive rejection. Look carefully if it eats away wanted data (usually stars) and go to the setting that is just right. Use a few frames to test (like 20) if you want to get a good idea for a larger dataset. If that still doesn't work well, you'd really have to get that data out indeed.