>>2681584The sky is moving really fast through a 500mm. You will need a tracking mount to shoot any deep sky object with it. With just a tripod, the moon is your only option.
You can see M42 without a scope. Its one of the only big, bright objects you can shoot at any focal length. (here a quick snapshit with the 55mm kit lens) Check the pleiades too.
But yeah for your 500mm, you will need tracking equatorial mount to do exposures longer than 1 second.