The A6000 certainly seems to be pretty good, and I'm looking at it too, as the 7's are out of my reach at the moment.
They seem lightweight and fast, and I've seen some good astro images come out of them.
I have used Nikon DSLRs on my ED80 for a while, and they produce good results but they are fairly heavy. You may need extenders to get it into focus though, so factor that in to the overall cost.
Someone posted this on here, using an A6000.
http://www.iceinspace.com.au/forum/s...d.php?t=132125
Looks promising
Good luck
Bob