A camera and lens can be mounted "piggyback" on top of a scope on an equatorial mount.

Piggyback astrophotography means you put your camera on top of your telescope and let your mount track the stars while you shoot long exposures with the camera's lens.

Besides a barn-door tracker, it's another easy way to get into long-exposure tracked astrophotography if you already have a telescope and mount.

Use the same camera settings and procedures that we discussed in the previous section for barn-door tracker photos.

A ball-and-socket head is used to hold the camera and lens on top of the scope. If your scope has mounting rings, you can usually attach the ball head easily with a 1/4-20 bolt.

If your scope only has a dovetail foot that mounts the scope, then you may have to scrounge around to find a ring that is the same diameter as your telescope tube to mount the ball head.

The Milky Way runs from Sagittarius, at the bottom of the frame, up through Scutum, and into Aquila at the top of the frame. It was taken with a Canon EOS 1000D (Digital Rebel XS) and 24mm fixed focal length lens riding piggyback on top of a 70mm refractor on a polar-aligned equatorial mount. The 60-second exposure was taken at f/4 at ISO 1600 with a custom white balance set in the camera. It was taken at a reasonably dark-sky observing site about 1 hour outside of the city of Philadelphia.

You can even remove your scope completely and take off the counterweight and mount just the camera and ball head on a dovetail plate. It may be a little unbalanced, but most mounts should be able to handle this.

Once you've got the camera mounted, you can easily aim it anywhere in the sky with the ball head, you don't even have to change the orientation of the scope or mount. The mount will track the stars to compensate for the Earth's rotation.

With an equatorial mount, it must be polar aligned reasonably accurately, although this is not extremely critical. With an altazimuth mount, you will be limited in how long you can expose due to field rotation.

Piggyback - The Bottom Line In piggyback photography, your camera rides on top of your telescope as the mount tracks the stars. It is very similar to using a barn-door tracker, except most equatorial mounts have a motor that turns the polar axis automatically.