You will be able to see comets. Do not expect your images to be anywhere as nice as the ones you see from the Voyager spacecraft. Galaxies will tend to look like bright blobs. You will also find that the colors you see are considerably more muted than the pictures you see. This is because our retinas work by having two different types of light sensitive organs, rods and cones.
Rods are very sensitive to dim light, but relatively useless for color vision.
Cones are the opposite. Thus when looking through a telescope you are using your rods, and you aren't seeing a lot of color.