John,
Astrophotography is a niche subject and, as things typically go with photography, it can be an expensive niche to get into.
What was it that you read which makes you think the NEX cameras can’t do it well? I can’t imagine it was to do with the sensors… the NEX 6 and Nikon D7000 share the same Sony-made sensor, and Sony is making some of the best sensors out there right now. Maybe it was to do with the native lenses? I could understand that.
The lens is going to be your real challenge. Wide FAST lenses are not a common design; they’re big, heavy, and expensive. By fast I mean f2.0 or f1.4. In the Native NEX line you have some wide lenses, and some possible lenses of varying price and quality…
Zeiss Touit 12/2.8
Sony 16/2.8
Sigma 19/2.8
Sony-Zeiss 24/1.4
Sigma 30/2.8
Zeiss Touit 32/1.8
The Sigma 30 might be worth trying out, just due to its outstanding performance and value… but not sure if it’s wide or fast enough for your needs. The Zeiss lenses are nice, but very expensive.
You’d probably be better off looking for a legacy SLR lens, such as the Canon FD 24/2.0. You should be able to find one for $300 or less. This lens can be mounted to the NEX bodies via an adapter, possibly Nikon bodies too (not sure about that, I do know it will NOT adapt to Canon EF mount).
Here’s a spreadsheet I made a couple years ago that lists prime lenses, weight, and approx cost on the used market. All of those lenses will mount to NEX (E-mount) bodies by the way.
I’d suggest you register on a photo forum that has an astrophotography group and ask them about recommended lenses. You’ll probably get some really solid advice.
edit: Josiah responded after I started my reply… that linked article is excellent.
