First light with new ZWO ASI533MC-Pro!
This project was not intended to be anything more than a test of the new camera, but I was very happy with the results nonetheless. I wanted to see what kind of quality was achievable with half the total integration time of my
previous 2022 M33, so I collected 6 hours RGB and 6 hours of Ha. It's hard to quantify the improvement as there are many variables at play, but I'd say it's easily twice the signal and considerably better detail than twice the time on my Canon DSLR.
I have been experimenting with exposure times on the new camera, and this image is a combination of 12s, 40s, 60s, 120s, and 180s for the L-Pro, and 120s, 180s, and 300s for the L-eXtreme. I found a spreadsheet which recommended 12s exposures for the L-Pro based on the SQM of my Bortle 7 (let's face it, Bortle 8) sky of 18.5 SQM. For whatever reason (probably having more to do with backlash while settling after dithering on my CEM26 than anything else) the 60s exposures seemed to be the sweet spot after I stacked each exposure bracket individually. Moving forward, I'll be sticking to 60s for the L-Pro and 180s for the L-eXtreme.
The last time I tried to integrate Ha data into RGB I had a heck of a time trying to do continuum subtraction.
SarahMaths Astro has an excellent
two-part tutorial on M33 which integrates
Pixelmath from
VisibleDark where the continuum-subtracted Ha image is used to create a mask for the RGB image that you are adding Ha to, but the un-subtracted Ha is added to the masked image which lead to a much better result than trying to add the continuum-subtracted Ha. Sarah also uses LinearFit to prepare the non-linear red channel for subtraction, which I thought was really clever, as it's normally used on linear data.
Long and the short, I am SO glad I upgraded, and very appreciative of the
feedback from the AB forum which helped make the decision.
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