To the extent possible, FX lenses used on a DX body will give you more flexibility down the road. They also are going to crop off the outer edges of the frame, so image quality is better than the same lens on an FX body.
The 17-55 f/2.8 is certainly a very good lens, but it was released in 2006 and lacks VR. I believe it has been discontinued, so parts - the AF motor in particular - could be a challenge. Buying used in the $450 range negates some of those issues, but I would not pay more. I prefer the 16-35 which is still in production, has VR, and is very good on DX. It also is a nice wide lens for FX. It is f/4 at the long end, but wide enough for astrophotography. You could also consider something like the 20mm f/1.8 - another full frame lens but a fast lens that is pretty good for astro. My preference of the DX lenses is the 16-80 - a very good lens, relatively recent release, and a good price point. With all these lenses, buying a good used copy from a known person is a good approach. I used to find the 24-70 lenses were not wide enough for me on DX cameras, so I always needed to carry a wide zoom or prime in addition to the 24-70. It's very good on an FX kit.
The 17-55 f/2.8 is certainly a very good lens, but it was released in 2006 and lacks VR. I believe it has been discontinued, so parts - the AF motor in particular - could be a challenge. Buying used in the $450 range negates some of those issues, but I would not pay more. I prefer the 16-35 which is still in production, has VR, and is very good on DX. It also is a nice wide lens for FX. It is f/4 at the long end, but wide enough for astrophotography. You could also consider something like the 20mm f/1.8 - another full frame lens but a fast lens that is pretty good for astro. My preference of the DX lenses is the 16-80 - a very good lens, relatively recent release, and a good price point. With all these lenses, buying a good used copy from a known person is a good approach. I used to find the 24-70 lenses were not wide enough for me on DX cameras, so I always needed to carry a wide zoom or prime in addition to the 24-70. It's very good on an FX kit.
