Revision as of 00:34, 24 April 2018 by Vincent (talk | contribs) (Slewing interfaces: moving mcmt)

Amateur astronomers are sometimes very skilled and creative, but also want to enjoy astronomy without buying expensive devices. This page tries to list active and open source projects that offer alternate solutions to market products, for lower cost or higher quality.

Alternative astronomy hardware

For focusers and telescope mount control, the general idea is to add some stepper motors that are accurate and powerful enough to do the job, mount them somehow with a 3D-printed or metal-bent support, use a microcontroller and motor drivers, and finally develop the interfacing software. In many cases, the motors are better and cheaper than those found on the market devices.

Using belts instead of gears is quite popular and cheap these days too, and helps reducing backlash and periodic error.


Arduino focus controller pro, a stepper motor focus controller (DIY) based on Arduino Nano/Uno. An updated version can be found on github, called the ArduiStepFocuser.

Telescope mount motor control units

To be able to control your telescope mount with a hand controller or a computer, it needs to have two things: motors and a control unit. Solutions on the market are at least $400 for a small automatic slewing system, called GoTo.

Slewing interfaces

For smaller mounts like EQ3, EQ5 or EQ6 and similar mounts, which covers entry and mid-level amateur telescopes, see the AstroEQ and OnStep projects. For larger telescope, the MCMTII may be your solution.

OnStep has been reported to be more active and more versatile than AstroEQ. The max version can handle 4 stepper motors, 2 for the mount and 2 for focusers or field rotator, useful with altitude/azimuth mounts. It can accommodate several stepper drivers and stepper motor models, if time is spent to configure it properly. It is also based on the Teensy microcontroller, it is more powerful than an Arduino Mega. See also OnStep github.

An alternative design for the max version can be found here. Differences with the official version are:

  • DIM connectors instead of RJ12 for motors 3 and 4
  • No access to Teensy outputs aux5 et aux6
  • An extra diode against polarity inversion (decreases voltage slightly)
  • Removed the 2 capacitors on the PEC and limit outputs
  • Added a jumper to select third and fourth axis and fan voltage
  • Grounded holes at each corner of the PCB
  • Ground plane on both faces of the PCB

Another alternative called TeenAstro can be found here and is discussed in French here. It comes with a nice box and a hand controller, aims to be more robust than official OnStep hardware.

To help configuring OnStep, a graphical settings generator has been made.

Guiding only interfaces


Weather station

A proper weather station that can detect cloud coverage and rain, which is mandatory for remote or automatic observatories, costs on the market at least $350.

Two approaches seem to exist for the cloud coverage: infrared sensor and a Peltier device that measures temperature difference between the ground and the sky. Here is an article that explains how the infrared sensor works and implements it with an Arduino and the MLX90614 sensor ($20).

Several ways of detecting rain exist:

  • optical, similar to what is used to activate the wipers in cars. This makes reliable and cheap sensors, $59 here:
  • conductive, the cheapest rain sensor found uses this, on amazon. Here's an page on how to implement this, the sensor costs about $4 with its module. Many other models exist on component sites.