The Heart Nebula (IC 1805) and the Fish Head Nebula (IC 1795)

I'm still amazed myself! Of course, the astro camera performs well and so does the processing. I think with a monochrome camera and separate SHO filters, the result could be improved even further. The signal-to-noise ratio would be better, and there would be no chromatic aberration.

Does chromatic aberration become noticeably apparent with the L-eXtreme?

Yes. There are two bands there, red and green. If you focus on the red, the green is slightly out of focus, and the stars appear bloated. And vice versa.

Understood. I want to experiment with my Takumar lens. It's sharp, but shows chromatic aberration. A workable option is to capture hydrogen and oxygen separately with refocusing.

It's too long and inefficient to shoot separately with a color camera this way. Stars can be adjusted during processing, rather than wasting precious clear skies. I focus on hydrogen, and this is how it turns out.

More precisely, with this processing, I remove the stars from the image and only take them from the hydrogen channel.

I split it into channels and processed it in the Hubble palette, as if from a monochrome camera. The sulfur channel mimics the luminance channel. In the comments for the North America Nebula, there are links to several processing videos.