ASCOM telescope focuser with Arduino

Another step has been made to have automated astrophotography setup – the focuser. SharpSky project was successfuly implemented in my second version of Astrohub, however this Astrohub has been made to work with DSLR. When I purchased ‘real’ CCD camera (Atik 314L+) Astrohub idea needed to be adjusted. I decided to built my own ASCOM controller focuser based on Arduino board. I have choosen Arduino Nano board because of its small size.

In the photo you can see Arduino Nano placed in the PCB. Under the Arduino there are hidden: L293D stepper and buzzer. Sockets at the PCB edge are for stepper motor, rotary encoder and DS1820 temperature sensor. At the same PCB there are two voltage regulators – for USB hub and for stepper motor. The project is available at page – there you will find ASCOM driver installer, Arduino sketch, required libraries for Arduino (Dallas Temperature, 1-Wire, Accel Stepper and others), all source code and quite extensive documentation, so I encourage to build your own focuser if one would like to – it is not rocket science at all 🙂

foc_3ASCOM driver was developed using available ASCOM templates. Implementation was made just to fulfill ASCOM IFocus2 interface, no additional bells and whistles. At the driver setup window you can set all the values required for the focuser to work. Focuser with driver was tested with Maxim DL software ( and it works perfectly ok. Focuser features are:

  • absolute focuser positioning
  • halt command
  • temperature focus point compensation
  • manual focus control using rotary encoder
  • stepper motor PWM duty cycle when motor not moving (prevents motor rotation under heavy focuser loads)
  • driver level backslash compensation (although its advised to use controlling application backslash if available)
  • telescope autofocus capability using 3rd party software like Maxim DL, or FocusMax
All project components were tested in ‘lab’ conditions and now are ready for field tests as soon as weather will be ready as well.

20 thoughts on “ASCOM telescope focuser with Arduino”

  1. Hi Andrea,

    I have little experience with such coupling 🙁 I always recommend to use dedcated gear box like in robofocus or couple with microfocuser shaft. Friend of mine tried to control his telescope with stepper directly coupled to main axis, but he use large motor and 1/64 microstepping and he claimed it works ok. When you use microstepping you need to remember the less microstep you work with the less torque you get.

  2. Hi lukasz, I'm planning making your focuser to fit my williams optics. I found schematic on GitHub. do u have a bill of materials available for the eagle files on GitHub.

  3. Super, thx, I will have a look. Are you still using the focuser or your setup ? Also, I don't suppose you have the PDFs in English do you

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