Alan Dyer in its website about astrophotography has put the recent Sony A7 Mark III into test for astronomy shooting with very extensive tests on low light, noise, color fidelity and comparing it with similar priced full-frame cameras: the Nikon D750 and the Canon EOS 6D Mark II.
The Sony performs very well, on par with (4 year old) Nikon D750 while offering also low-light real time video since the shutter speed can be as low as 1/4 sec but requiring an external intervalometer (quite a miss).
Canon sensor show less dynamic range and more noise but is more sensitive to the reds of some galaxy.
But the most awaited was about the so called star eater issue: all Sony A-series cameras with exposure time of 4 seconds or more trigger a noise reduction process that "eats" away the faint stars and it is NOT possible to disable it also if shooting RAW. That's a major stopper for astrophotography though a workaround has been found - shooting in continuous mode, though precision drops to 12 bit and not full 14 bits.
Well, Alan Dyer has found that in A7 III the issue is mostly solved! There is still some softening of small stars with times of 4 seconds or more but the effect is surely no more a stopper. Finally!
Read all the tests at this link. Also the card of A7 III in our camera archive has been updated with this interesting link.
It would be good that Sony would provide a firmware upgrade for previous full frame cameras (Sony A7RIII, Sony A9...) to fix this, but Sony is not behaving like Fujifilm that really cuddles its customers with continuous and features-full firmware upgrades. Let's hope...