Just going to show a few crops here as you can get more detailed reviews elswhere but here are some facts:
- both photos were shot in pretty much the same location (talking about 2km distance here) but we are not really looking at light pollution in this case
- both photos were shot on the Samyang 14mm F2.8 (also sold as Rokkinon in some countries) – the a7iii using the Sigma MC-11 Adapter
- both cameras used the same exposure settings, ISO 3200 and 25s
- just for the record – its APS-C vs full frame.. so yeah less star trailing on the Sony
Apart from the sensor of course the photos were shot with similar parameters the M5 with High ISO and Long Exposure Noise Reduction
The Images are both unedited, as is when imported into lightroom with only the lens profile and lens CA corrections applied.
I rarely shot on ISO 6400 on the 500D and the M5 as it became significantly worse but will post some 12800 on the a7iii in the future.
Currently ISO 3200 is my go to setting for astro @ 25s the only real way to get better conditions is to move into a darker light zone which will hopefully be done in 2022 with the next milky way season.