A basic, inexpensive 35mm or 50mm lens is perfect for shots of Orion, the Summer Milky Way in Sagittarius and Cygnus, and many other wide-field areas of the sky. Armed with a roll of 800-speed film you can achieve very good results right away. Start by picking a nice, bright region of the sky. Orienting your camera is usually easier piggyback than when you are shooting through the scope, because you are more likely to see what you are framing. Focusing is usually as easy as setting the camera's lens to the infinity setting. But, always double check! Some lenses focus past the infinity mark so that the stopping point on the lens is not at infinity. Other lenses may not be calibrated correctly and the infinity marking may be incorrect. A ten minute exposure at f/2.8 is plenty to pick up the bright nebulae in Orion and Sagittarius. If your lens opens up faster than f/2.8 (say, f/1.7 or f/1.4) stop it down to at least f/2.8. It is tempting to go faster, of course, but lens aberrations tend to be horrible at the edge of the field in such fast systems. After you get back your amazing first shots of the Milky Way, the next step is to zoom in a little closer on some interesting objects. A 135mm lens is a good choice. A 200mm lens is good too. 300mm lenses tend to be slow if they are inexpensive and expensive if they are fast, so this selection might be better for when you have improved on your technique. A 200mm f/2.8 lens will require additional counterweights on a fork-mounted telescope, by the way. I learned that one the hard way and ended up with a photograph of the "flying" Pleiades! When using a longer lens, guiding will be required. 135mm is usually considered the upper limit for unguided photography. Guiding piggyback is easier than guiding prime-focus shots. When shooting at 135mm focal length and guiding at 2000mm, for example, you have a fair amount of room for error. The more forgiving nature of piggyback photography is why I highly recommend it as a way to begin learning all the various techniques of astrophotography before moving on to more advanced techniques.