[QUOTE=Retrograde;1319788]Thanks Greg.
The K-5, despite basically being a 5 year-old design now, seems to be quite good overall when it comes to noise:
http://www.brendandaveyphotography.c...ensor-testing/
It obviously doesn't have the photon-grabbing pixel size of some of the full-frame cameras out there however.
That 16mp APS Sony Exmor sensor is in quite a few cameras from Nikon to Pentax to Fuji X and was a hugely successful sensor. The latest and greatest is the Sony Exmor 24MP APSc with copper wiring (CMOS sensors typically use Aluminium wiring). As in the A6300, A6500 and Fuji XT2, XPro 2, XT20. Its a nice sensor and slightly better noise performance but not a lot of difference for astro work so no need to upgrade there. The Nex 6 is the same 16mp Sony Exmor sensor.
Greg.