Did I created an artefact with light pollution filtering

Processing Deep Sky IC1318 IC Objects
3 replies•103 views
Paul Bédard avatar
Paul Bédard avatar
On this photo of IC1318 in SHO, I tried light pollution correction in AstroPixelProcessor. I ended up with those EW orientated reddish crescents. Are these crescents an artefact of the correction or they really exist. Without the light pollution correction, red crescents are absents. Photo was taken with a Redcat 51, oPtolong L-Ultimate filter and a ZWO ASI533MC Pro Color camera. 
Thanks for your advices. 
Helpful Engaging
andrea tasselli avatar
andrea tasselli avatar
You have no reason to correct for light pollution with a filter such as the L-Ultimate, so just don't.
Paul Bédard avatar
Paul Bédard avatar
andrea tasselli:
You have no reason to correct for light pollution with a filter such as the L-Ultimate, so just don't.

That is a valid point. I normally don't.
But I thought that some artificial light might not be fully removed by the filter.
andrea tasselli avatar
andrea tasselli avatar
Unless you shine a light directly into the 'scope, no, there is nearly nothing there other than signal. Assuming good flat fielding technique, that is.
Related discussions
Crescent Nebula raw data available for processing - 21 hours collected
Hello all, The time has come again to offer up some of my raw image data for anyone to process if you’re up for it, specifically my 2025 acquisition of the Crescent Nebula in Cygnus. I captured this in a relatively narrow FOV with my Celestron C6 sco...
Raw IC1318 data processing experience relevant to troubleshooting author's correction issues.
Jan 7, 2026
Keep or sell my Optolong filters?
Hi, I have Optolong SHO filters with 6.5nm and 7nm 36mm since 2018, and i used them several times in the past without nice results due to LP in my area, and later when i added 3nm filters i no longer using those Optolong 6.5nm/7nm filters anymore, bu...
Direct experience with Optolong filters and light pollution correction challenges.
Aug 22, 2025