Ha with LRGB or RGB

[RobF (Rob)]

I'd be interested to learn what others are doing for Ha combines on nebs and galaxies? Pixinsight has gained a few Multichannel Synthesis scripts in recent years, but I always feel like I'm in a 747 cockpit trying to figure out how to start the engines with these! Almost always go back to doing pixel math to add Ha into red and 10-15% into blue.

Try to avoid adding Ha into lum, but experiment with it on some objects. Of course getting nice false colour NB images is another challenge, but I'm particularly interested in using Ha to boost LRGB or RGB images here.


What do you do? Have you changed your approach at all in recent years?

[RickS (Rick)]

Rob,

I don't like the PI scripts much since I can't tell what they're doing without reading the source code (or the French documentation), and I'm too lazy for that.

I've found I get the best results from using LinearFit to make the data compatible (e.g. fit Ha to Luminance) and PixelMath for combining Ha and Lum or adding Ha to Red and Blue. The usual problem of adding Ha to Lum resulting in pink/salmon colours is not a big issue if you fit the combined Lum to the original (don't forget to use RGBWorkingSpace to set a 1:1:1 space for luminance extraction) and play with the saturation curve or CIELAB *a and *b if needed.

Cheers,
Rick.

[RobF (Rob)]

Thanks Rick. Good to see someone else find those scripts tricky. I'd feel better if you could tweak sliders and see the output in realtime, but it seems pretty hit and miss. Linearfit was something I've only started using regularly of late and ashamed I hadn't used it much more in the past - really does a great job of balancing R, G and B. I'll do as you say and try it for some Ha/Lum.

Those CIELAB colorspaces? are freaking me out though. Have always managed to find an excuse not to go anywhere near those??

[RickS (Rick)]

Originally Posted by RobF

Those CIELAB colorspaces? are freaking me out though. Have always managed to find an excuse not to go anywhere near those??

LAB is pretty cool, albeit freaky Rob The nice thing about it is the ability to tweak lightness or colour independently.