This project was a test of an old Canon EF 300mm f2.8L (1994 serial). I've had this lens for some while and a year ago used it for Markarian's Chain https://www.astrobin.com/17pt3l/B/ made pretty sharp images on just my Skyguider and 40-50" exposures, in not much more than an hours time. Problem was the lens suffered from severe coma (or whatever other optical aberrations, i'm not an optics expert) which was quite distracting. Stopping way down helped, but the main reason for this big lens was that big ~107mm aperture and fast f/2.8 speed. I already had a much smaller 300mm f4L IS that shot pretty good wide open and way easier on my little tracker. Problem with the f4L lens is that it wouldn't readily accept telescope filters like my 2" NBZ. The f2.8L lens would, except that mine came with the gel filter holder instead of the screw type holder. I gave up on this lens for a while.

My thought was with narrowband imaging I could hopefully produce a good result of nebula and make them starless, so no worry about coma! And then it dawned on me once I got better at processing I learned how to recombined rgb stars so I could shoot stars stopped down and add them back in. Well it took a year of searching to find the original 48mm screw filter holder for my lens. Now I can slip the NBZ filter right in! I used my DIY full spectrum modified Canon 60D. Also made an aperture mask to get those sharper stars with a seperate unfiltered session. I cut a hole of about 52mm or so, giving me about f/5.6 or so. I maybe could go bigger, stars were perfect and I don't see any hint of coma (will have to check with full frame camera though). Even at f/5.6 and the 60D I was able to make pretty good RGB stars in an hours time (I was planning for 2hrs, but... clouds). 

This warrants some further testing, maybe I can find the max size to shoot with minimal coma, and see if it also sharpens up detail in the nebula. Maybe it will be worth stopping down a bigger lens, rather than using the smaller lens, if the optics are better and images are improved. I'm happy with how this turned out for sure, but was hoping for a bit more sharpness for this length of acquisition at f/2.8. Perhaps my old 60D is the limiting factor though.

So to summarize: I shot just shy of 10 hours with NBZ duoband filter @f2.8. 480" shots with no/little moon, backed off to 300" shots when the moon was greater than 30%. Forgot on my last session with no moon to go back to 480", whoops. I stacked in Siril, extracted Ha and OIII. Made starless copies of them then used Siril to make HOO composite of starless Ha and OIII. Then I shot a short session of 60" @f5.6 with only UV/IR cut for RGB stars. Created a stars only image, which I added to the HOO image.

As a Gemini myself, this has special meaning. Well I'm not into astrology whatsoever, but would like to think there is some special connection to the Jellyfish ;-)
Enjoy! Cheers!