DIY Barn Door Tracking Mount
A barn door tracker is a simple motorized mount that counteracts Earth's rotation during astrophotography exposures. It allows exposures of several minutes with a DSLR and wide lens without star trailing. Total build cost is under 80 dollars.
3Minutes
30Minutes
Design the Mount
Description: The classic single-arm barn door uses two wooden boards hinged at one end. A stepper motor turns a threaded rod at the correct rate to match Earth's rotation. Use the isosceles design for accuracy over longer periods.
Build the Tracker
Description: Cut two 30cm boards and connect with a piano hinge. Mount a stepper motor and motor driver (ULN2003) on the lower board. Thread a 1/4-20 rod through the upper board at the calculated pivot distance (28.65cm for a 1 RPM motor).
Polar Align the Tracker
Description: Align the hinge axis with Polaris (northern hemisphere) before each session. Use a polar alignment scope or a phone compass and inclinometer app. Accuracy within one degree is sufficient for wide-field photography.
Build Checklist
Source all parts (see Parts.chext for full list)
Cut and sand both wooden boards to size
Drill motor mount and threaded rod holes precisely
Wire the stepper motor to an Arduino and ULN2003 driver
Program the Arduino with the correct step rate for your rod pitch
Test tracking accuracy with a 2 minute star exposure before dark
The most critical measurement is the distance from the hinge to the threaded rod. A 1mm error causes drift over long exposures. Measure twice, drill once.