This is one of my recent photos. It's a rather simple setup comprising a Canon 5D Mk2 and a Canon 300mm f/4 Tele plus 1,4x extender. I'm not exactly ecstatic about the quality of this lens/extender combination but what I am happy with is the quality of the sky ~100km away from my home.
ISO 800, 12x300s lights, 30 darks, 20 flats. My typical Spartan image processing: Stacking and automatic color correction in Regim, spread in Gimp. And that was it.