Q) All the posts about this HaRGB combination just talk about the Ha and RGB. Haven't seen too much mentioned about L. Does that get added at the end, after Ha introduced into the R? Or when reference is made to the RGB, is that actually an LRGB image being referred to? I don't think so, because as I understand it, L is best combined with RGB after a bit of stretching?
A) Two options here:
1) You didn't capture L. Just put your Ha image as the L. You'll end with a Ha(Ha+R)GB.
2) You did capture L. You need to combine somehow L and Ha. Use pixelmath to reach the best results here. I recommend L + (Ha * constant) here.
Point 2 is a too short answer to me. Combine L and Ha some how, OK and then? In the tutotial from Harry Ha is added to the red channel. Then there is this two part LRGB video on the PI homepage, were the L part is added to the RGB image after stretch. This is total unclear to me, now. I think this Ha LRGB image stuff could need an additonal video tutorial ;-).