While for many nebulae with common names, I can understand the case for the name. For the Cave however, I just don't ... so be it.

The processing of this nebula turned out to be a bit more difficult than I initially expected. While I was capturing data for another object, I used the nautical twilight to collect data in the Ha. Once the other project was finished, I also capture LRGB. As it turns out, one has to pay attention to the moon phase. There's just too much nebulosity which makes it quite difficult to remove the gradient caused by the moonlight. As it's always a good idea to avoid broad band while the moon is bright, it's especially true for this object. The initial capture of the green and blue channel had so much gradient that any attempt to calibrate the image properly lead to psychedelic sky backgrounds. Hence, I had to wait for a clear night with little moon. Fortunately it took only two weeks for the moment to come and I could gather the G and B.

The data was sitting on my disk until recently. Triggered by the very good interpretation of the same object by fellow astrophotographer @Tom Gray, I had to process my data as well. There's the real chance that I might have forgotten the data.

The Ha data is clearly predominant. Nevertheless, there's still broad band data. Around HD216629 we can clearly see a patch of reflection nebula. Overall, there seems to be interstellar dust which is noticeable if one shoots in RGB, leading to a very slight yellowish tint after proper color calibration.

Processing this image makes me remember a conversation with @Brian Boyle about the processing of HaLRGB. Hence, let me summarize a bit how the data was combined:
The RGB is fairly straightforward which mostly provides the color for the stars and non-Ha data.
L and Ha were stretched and combined through averaging. The L contained nebulosity which isn't contained in Ha, so I wanted to have both worlds. Once L and Ha were combined, I used this as the new Luminance for the RGB data.
In addition, I created a starless Ha which I colored and screened onto the whole image, effectively saturating the Ha regions a bit more and adding a bit more contrast.

IMHO, there's no strict recipe for HaLRGB and it always depends on the object and the intention of the photographer. It's like cooking: a matter of taste.

Hope you like it!

CS, Björn