Piggyback

Dale Keller built this piggyback guider for astrophotography with a 35mm SLR camera.

The telescope is a 50mm refractor with a focal length of 600mm. A homemade crosshair was added to the 12mm eyepiece.

The fork is made of 1/2 inch plywood. The telescope cradle and camera mount are of aluminum. No machining was required for the cradle - just careful cutting, filing, and drilling. The cradle tilts within the fork on two 3/8" bolts.

The camera mount is hinged and a screw with a nut pulling against a spring allows the camera to move up and down in relation to the guidescope. The camera can be moved left and right by loosening it's lockdown screw.

The fork rides on a 1/2" shaft of allthread. This shaft rides on two ball bearings on angle brackets. The base is made of a 2x4 (the polar piece) and several 1x4's. The polar brace is angled at 40 degrees for Denver's latitude. Be sure you set this angle for your latitude.

The drive mechanism is a 1' arm with a 1/4-20 screw driving against a spring. The operator turns the handle slowly while guiding. This could easily be replaced with a motor drive.

Polar alignment can be done by sighting along the polar axis. A polar finder scope could be mounted above the polar axle to make this easier.

For short exposures (under 5 minutes) with a short to medium length telephoto lens, guiding is easy and fun. With a long telephoto or longer exposures, it can get tedious. The lack of a declination drive means you can't correct for atmospherics or misalignment in any but the right ascension axis. But it's simple and quick to build from scrap materials and a cheap telescope, and it's fun. And you can get some pretty nice astrophotos with very little equipment.