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M27 narrowband  


Neutron Star Customer
Joined: 3 years ago
Posts: 101
May 16, 2021 02:08  

Good Morning,

Recently, I had a fine 3-day stretch of clear weather, and after an investment of 6.5 hours, I have this nice narrowband image of M27 in 7nm Ha and OIII. I like APP's HOO2 palette because I like the colors, but more importantly, it does a fine job of preserving star colors.

A friend introduced me to LRGBHOO, but after capturing only 1.5 hours of LRGB, I was disappointed but not surprised. I lost the faint, delicate narrowband nebulosity in the outer shell. I need more broadband integration time, but I think that I may never be able to capture enough. Here is my reasoning. (If anyone sees a flaw in my logic, please speak up.)

Narrowband is great, particularly for those suffering from high light pollution. The "magic" happens because my filter passes through only 7nm of light pollution. Now compare that to a standard red filter that lets in 100nm of light pollution. In essence, the narrowband filter transports me from my so-so Bortle 5 skies to a Bortle 2 or 3 remote site. But with regular LRGB, I am stuck with the full Bortle 5 light pollution. The only way to overcome all of that noise from light pollution is to stack and stack some more.

Do you see the problem? Even after investing lots of time into LRGB, I may still lose that faint narrowband nebulosity. I would be happy to discover that I've committed an error in my logic. If not, are there other techniques I can use?

Thank you,


M27 HOO 2 Ha 7nm 51x300s b1 OIII 7nm 26x300s b1 CBG ST 15 3 25 SA 35 25 SH 4 5 AFF EX 100

Universe Admin
Joined: 4 years ago
Posts: 3955
May 16, 2021 11:18  

Yes I do see your problem with that, I must say I don't have too much experience with those palettes. I do think that it'll always be a compromise, because you always need to end up in the RGB space. Being able to combine very nice RGB stars with narrowband usually then requires a bit more processing than APP currently has I think. Luminance will also subdue colors, Mabula is going to look at that specifically to see if he can improve on that, for Luminance I would reduce that mix to about 50% or less, you can experiment a bit to your liking.

Regarding the bortle 5 issue, yes that unfortunately can't really be dealt with unless you want to go full photoshop trickery. 🙂 A darker site or way more data is likely the only way then.