DIY Telescope Clock Drive

Clock drives are simple tracking mechanism that move a telescope’s RA axis one rotation every one sidereal day (23 hours and 56 minutes) to effectively compensate for the Earth’s rotation. It allows precise tracking of planets, galaxies, nebula, and other sky targets.

Telescope clock drive controller based on L293D and Arduino Uno board

An inexpensive Arduino Uno board and L293D-based stepper motor driver can be used to control a telescope. Attach a stepper motor on a telescope’s RA adjustment knob, then find the correct motor speed that will match the movement of the sky. Below is a sample sketch for a simple telescope clock drive controller.

//Simple clock drive controller by Anthony Urbano 06 September 2021. It uses an Arduino Uno and an L293D.

#include <AFMotor.h>                  //Go to SKETCH > INCLUDE LIBRARY > then lookup "Adafruit Motor Shield Library"
AF_Stepper motor1RA(24, 1);           //Initializing motor's steps per one full rotation; Connect the motor to M1 port
void setup() 

void loop()
  motor1RA.setSpeed(100);              //Change the value to speed up or slow down the tracker
  motor1RA.step(1, FORWARD, DOUBLE);   //Motor takes 1 step forward; to reverse direction, replace FORWARD with BACKWARD

With proper polar alignment, a simple clock drive is capable of imaging deep-sky objects, such as the Flame and Horsehead Nebula. This image was taken with a telescope at 565 mm focal length.

Flame & Horsehead Nebula imaged with a telescope mount with a simple clock drive mechanism

Related links:
OnStep Go-To Telescope Controller
View all home-brewed DIY astronomy equipment

Night Sky in Focus 
© Anthony Urbano | Bacoor, Philippines

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