:INFO
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.


:COUNTER.half
3 Minutes
|
:COUNTER.half
30 Minutes

:PATH
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.

:PATH
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).

:PATH
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.

:CHECKLIST
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

:NOTE
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.