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LNC applicability to night to night gradient changes
I've been stacking a multi-night data set of Ha data of SH2-114. The first night there was no Moon present but on subsequent nights the Moon is present and at different angles relative to my target so when I stack I get a combination of several gradients in the final stack.
My understanding was LNC could address this by using the first night as a reference for what the background ought to look like and model this in the other images to determine the unwanted gradient contribution from the Moon.
So far I have enabled LNC when integrating and tried various orders and iteration limits but the final product clearly has a gradient in it.
Is there a way to use LNC to solve this problem and perhaps a tutorial about this specific application?
LNC will try to make them as similar as possible, but it's not going to take out big gradients. For that you use the Light Pollution Correction tool, you can use it once, save the result and then again if not satisfied yet. In the end, the moon will always drown out some data which can't be recovered, so usually people tend to separate data without the moon with data with the moon as separate integrations.
Thanks - I was just looking for a way to handle the gradient prior to the stack operation.
The light pollution tool did a nice job after stacking so that is good.
What about for different filters, Ha for one night and OIII for another night, if I use multi-channel processing with LNC, will the gradient from OIII affect Ha?
No, it shouldn't, it corrects the panels for each filter.