Build Your Own Star Tracker

Yes you too can take night sky photographs worthy of being published in your favorite astronomy magazine. Search for novae, comets, and asteroids. Amaze your friends! See what Carl Sagan means when he says billions and billions of stars!! You need just one one hour and $25 dollars and you can build your own star tracker.

The Principle

It takes 1436 minutes for a star to make a complete revolution around the celestial sphere. Recall the formula for calculating circumference:
If you drive a star tracker at 1 turn per minute with 32 turns per inch thread then:
             radius = 1436 minutes / (2 * π * 32) = 7.14208 = 7 9/64
Keep the angle small and use a 32 turn/inch thread 7 9/64" from the pivot, then you can track the stars.

Parts List

  • 1 Strap Hinge
  • 1 Dash Board Clock that displays seconds
  • 1 Small Goose neck lamp with red filter (of course)
  • 1 3 1/2" 10-32 Brass Rod
  • 2 1/2" 1/4 X 20 (NC) Bolt
  • 1 1/4" 1/4 X 20 (NC) Nut
  • 1 1/4" Lock Washer
  • 2 1/4" Fender Washer
  • 2 10-32 Tee Nut
  • 1 2" 10-32 Bolt
  • 1 1 1/2" 10-32 Bolt
  • 8 10-32 Nut
  • 4 #10 Lock Washer
  • 2 #10 Flat Washer
  • 1 1 1/4" Bushing (for 10-32 bolt)
  • 1 Knock-out disc from electrical box
  • 1 White Lid approx. 2 1/2" in diameter
  • 1 Paint Stir Stick
  • 1 Straw

The Expensive Stuff

  • Fully manual Camera (e.g., Pentax K 1000)
  • Sturdy Tripod
  • Pan Tilt Head

Odds and Ends

  • Drill
  • Small Circular file
  • Small Flat File
  • Velcro
  • Glue (Duco is my favorite)

The Details

The Main Hinge

Success or failure of your tracker is going to depend on your drive point. This is where your own creativity can come in. If you can think of a better way, try it, but mine works. Very accurately measure off 7 9/64" in both directions centered along each of the sides of the hinge from the center of rotation. Once you have the point, use a punch to make a small dent. Use a small (3/32") drill to start with, then finally drill the hole with a 5/32" on the top plate and 1/4" on the bottom plate. Drill a 9/32" hole for your tripod mount approximately 2 inches from the hinge on the bottom plate. Glue your Bic pen tip pointed inward on the top plate. Reinforce with washers. Glue a Tee nut pointed downward on the bottom plate. Carefully align it with your pen tip. If you keep the plates parallel and look through, you should see the pen point perfectly centered. Glue the metal electrical knock-out disc to the second Tee nut.

The Crank Assembly

Cut a 3 1/2" section off of the paint stirrer. Drill two 5/32" holes appropriately located to make a crank. Make a handle by putting the bushing, 2 nuts and a lock washer on the 2" bolt. Attach the bolt to the handle and fasten with a lock washer and a nut. Mark the lid with a 0, 15, 30, and 45. Add marks for five minute intervals if desired. Mount the lid and crank on the 10-32 shaft near one end with nuts and lock washers.

Tip Protector

Assemble the tip protector by fastening a 1 1/2" bolt to the end of the hinge with 2 washers and a nut. Put another nut near the top. This will be adjusted to protect the tip from being dropped on the disc when not in use.

Final Assembly

Thread the shaft through the Tee nut on the hinge. Thread a 10-32 nut from the top down to the hinge. Adjust this nut to provide a small amount of tension to the shaft. Glue the nut in place being careful not to get any glue on the shaft. The purpose of this nut is to carry the weight of the camera and prevent the Tee nut from being pressed off the hinge. Screw the Tee nut and disc on the shaft. Adjust the tip protector. Attach the clock to the underside of the hinge with Velcro. Attach the straw near the axis of the hinge with Velcro. Attach the Pan Tilt head to the top hinge. Attach the tracker to the tripod. 

Congratulations! You are done.

The author, Glen Gould, is an amatuer astronomer who used his star tracker to capture Comet Hyakutake in March 1996. The photograph was published in the book Comet of the Century: From Halley to Hale-Bopp.