Re: Spotting Scope & Tripod
As has been mentioned, the biggest factor in seeing anything at 600 yards is mirage. The Hubble would have difficulty at my range on a hot sunny day in the summer, as the mirage is just too great (we shoot over a swamp, so it is particularly bad). On overcast days, I have been able to make out 30 caliber bullets, and sometimes even 223 caliber bullets, at 600 yards with the setup below. Note that I use Shoot-N-C targets, which is the ONLY way you are going to have any chance at all of seeing your shots.
I use a
Celestron C90, which is a maksutov style telescope. It uses mirrors to fold the light path, rather than glass lenses to refract it. The benefits are that it is lighter and cheaper for similar optics, and these designs excel at higher magnifications. The downside is that you are limited in the lower magnification limit. The focal length is 1250mm, and the biggest eyepiece I found is a
Celestron Omni 40mm. This gives a magnification of just over 30x, which is just barely acceptable when mirage is really bad. Ideally, I'd be able to back it off a little more, but that won't happen with this scope. The flip side is you can even a 20mm eyepiece - which is still considered quite big as far as eyepieces go - and have a very usuable 60x scope. Light gathering can be an issue of course as the light gets less around dusk, but the 90mm objective helps.
For a tripod, I'm using a
Giottos MT9241. I bought it as a travel tripod for my DSLR camera, but it works great for my scope. Small enough to fit next to you comfortably in prone, large enough to shoot offhand, and large enough to keep thing nice and steady. I'm fit a
http://www.bhphotovideo.com/c/product/318594-REG/Giottos_MH_5001_MH_5001_3_Way_Pan_Tilt_Head.html Giottos MH-5001 3 way head on the tripod. I find I like the 3 way head better for shooting, as it is much easier to set each axis individually for a static target.
Everything above should keep you within your $500 price range total.