[Solved] Remove Light Pollution tool question?

Posted by: @roscoed

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I used to swear by the lpc-cbg step.  Now when I apply it to my newly-acquired ZWO Duoband filter (HA and OIII) imagery it's doing weird stuff.  Here are two examples of nebula taken with this filter.  In both, the left frame is the original, post integration/stretch.  The right one is after the LPC-cbg step.  Based on other pictures I've seen, I believe the pre-LPC versions are more representative.  In each case one quarter of the picture is turning red.  Is this a natural result of this type of narrowband image where it seems to be correcting the "lack" of red in the otherwise normal areas?

 

 

 

@roscoed, this actually shows that there is more nebulosity in your data than most users show in their images. This happens a lot with h-alpha nebula that have weak nebulosity extending further away. The background calibration (the -cbg part) is responsible for showing how much nebulosity there actual is in the data. If you perform Remove Light Pollution correctly, H-alpha signal is not created out of the blue 😉 But if you misperform Remove Light Pollution, then weird gradients can occur but these can be red/green/blue, not just red normally. Maybe you need to redo the Remove Light pollution and place the area select boxes differently? If the outcome is the same, than it makes it more likely that the H-alpha signal is there.

Mabula

Thanks!

I can't rule out I'm doing it wrong, but given that I can't find any guidance on what "correctly" is I have no idea.