I'd also agree with getting a dob initially. For $500 you could get an 8" dob with a couple of eyepieces, and it will really open up the visual side of astronomy.
If you are really keen on photography, then the only reccomendation I could make is to spend the $500 on a motorised equatorial mount, and stick your camera on it and take some widefield photos through your camera lenses. Or simply use your camera and lenses to take photos of planetary conjunctions and the like. Site Admin Mike has made APOD (NASA's Astronomy Picture Of the Day) a couple of times with these types of photos
example