Autofocuser 3

We are striving to provide the astrophotographers across the globe with affordable autofocusing solutions, which can greatly improve the automation aspect of the capture process.

Based on your feedback and our experience with AF1/AF2, we have developed an upgraded version of our autofocuser. It is based on newer technology, boasting a stealth drive feature for minimal noise and vibration. Apart from the smoother motion, it also provides more accurate movement with microstepping down to 1/256. Enclosure was also optimized for easier assembly, but of course retained backward compatibility with every existing adapter. AF3 is also ASCOM/INDI compatible, just like AF1 and AF2.



  ASCOM supported
  INDI supported
  INDIGO supported
  custom step size
  speed control
  current control
  hand controller (optional)
  temperature probe (optional)
  settle buffer option
  compact design (44.5mm x 48.5mm x 50.2mm)


For software downloads, please visit our SHOP
power adapter: 12V - 14V MAX (1A min) with 5.5mm x 2.1mm plug (not included)
connectivity (not included): Mini USB cable OR Micro USB cable (2020)

AF1 vs AF2 vs AF3




Discontinued with 1.2020 (except bugfixes) Yes Yes
Custom opensource firmware
ASCOM driver
INDI driver
INDIGO driver
TheSkyX Pro X2 Focuser Plugin
size (mm) 44.5 x 48.5 x 49 44.5 x 48.5 x 57 44.5 x 48.5 x 50.2
weight (g) 168 172 170
Existing adapter (3D printed adapter, L bracket, timing belt) 20€ 20€ 20€
Custom adapter 40€ 40€ 40€
USB connectivity Mini USB Micro USB Mini USB/Micro USB (2020)
Stealth drive
No gearbox (no backlash)
Wifi remote control
Temperature probe (optional - 15€)
Manual remote controller (optional - 20€)

Microfocus knob belt drive

By connecting the motor pulley directly to the microfocusing knob, we are trying to make attaching the autofocuser as seamless as possible. This method is quite unintrusive, as it does not require focuser axis knob dissasembly, attaching directly to the axis shaft via coupler, etc. In our experience, belt slipping is a non-issue due to little force required. If the belt tension is appropriate, autofocusing works like a charm. This approach has following pros:

  • compact mounting balance-wise in comparison to shaft mounting, which protrudes away from the telescope tube.
  • driving microfocusing knob does not require a lot of force. This means that autofocuser motor can be quite small and does not require gearbox.
  • if you racked the focuser in/out and keep on moving the motor by mistake, it is not strong enough to damage any parts of the focuser shaft (motor starts skipping steps). With coupler connected to the focuser axis directly this could not be the case. Usually stronger motor or even a gearbox is involved to drive the shaft directly. This could result in damage to the gearbox, coupler or in worse case focuser itself.

William Optics cats series

The brand new William Optics RedCat telescope is an alternative to the widefield lens shooting with 250mm of focal length. With the helical focuser, focusing can be quite time consuming process even with the Bahtinov mask (especially with narrowband filters). Our autofocuser will save you time and frustration by providing pinpoint stars on your beautiful photos of the cosmos.

Listening to your feedback and following the new developments from William Optics, we have refreshed our line of cat series autofocusers. You can now choose one of the main 2 options - dovetail kit and ring kit.