2018: 4 hours Ha, using 48 x 5-minute subframes
2023: 2 hours each of SII, Ha and OIII, using using 30 x 4-minute subframes

Why do astrophotographers image the same objects, over and over again?

People often ask me why I image an object again, if I have already taken a photo of it.
It is a fair question.
My answer:
- Things change: Equipment, technology, software and skills.

I was happy with my image of the Bubble nebula, (NGC 7635, Caldwell 11), in 2018, using the best equipment, technology and software I had at the time.

But things changed. I got a beefier mount, slightly bigger telescope, and a different camera. I also have more filters with a narrower bandwidth.
The guide software now uses multiple stars, and the image capture software (I use APT) has automation, to improve efficiency and prevent me from making mistakes.
I now have an electronic focuser that the image capture software instructs to refocus, based on HFD and FWHM at regular intervals (or by temperature change, or time or number of images).
And the processing software now has weighted integration, AI deconvolution, AI noise reduction, AI star removal, etc.

When I got into astronomy, around 1970, I never would have imagined this was possible, from my own backyard, with equipment I could afford to own.

We live in amazing times.