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Ha is only one component in an image. If you collect just Ha you will only have a grey image that lacks a lot of detail. Ha can be bright but lacks definition. RGB + Ha is a normal process with Ha added to the Red Channel or used as a luminance in Lab Colour mode. There are probably other options but I haven't found them yet. Some RGB filter sets have frequency notches in their coverage which does reduce some LP effects.
Ha also works with OIII and SII for a Hubble palette image. In that case RGB is not used. That combination gets around most light pollution problems but does make for longer exposure times because you are capturing such a small part of the spectrum. Ha normally gets assigned to the Red channel, OIII to Green and SII to Blue in that case.
I normally try to capture in all 5 channels, LRGB and Ha unless I am specifically looking for particular Ha targets where L can be a waste of time. It may only be a couple of captures, as much to test focus and get a full picture of my target in grey of course. It is often not used in processing later.
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