Upload & Sell: Off
As long as I'm posting here, I'd also like to share my findings shooting astro from a suburban back yard...
I have had excellent results shooting at f2.8, 20s, at ISO 8,000. I then reduce exposure in LR to taste. I have previously shot at 3200, but just didn't pick up those fast-moving meteorites. Only the most bright couple of stars show some blowout at this exposure.
I noticed that when the stars trail a bit at 20 seconds (vs 15s), that LR gives more consistent star color. This may be due to atmospheric distortion, or the noise reduction action on pixel-sized stars...
With minimal NR, ISO 8,000 looks better than 3200 with optimal NR, with the additional light allowing negative EV in post, and they also better hide impulse noise at the pixel level.
The 5D3 at 8,000 is way better than my very old 1Ds at 1250!