The system fits on all EQ-5 mounts; SW EQ5, Celestron CG-5, Bresser Exos II

Based on Nema 17 stepper motor positioning system, this kit includes all necesary to fully control your mount, hand controller is optional but not needed, package content:

  • 2x Nema17 0,9º Step Angle Stepper Motors (5,4VDC, 0,9A, 36Ncm nominal Specs), installed on brackets.
  • 2x 16 teeth and 2x 40 teeth pulleys, 2x belts
  • 2x Flat RJ45 cables 1 metter long.
  • Main Drive with TMC2130 stepper motor drivers installed, 2x antenna for BT and WiFi.
  • 2x reusable nylon fasteners, system mounting screws.


  • Permanent PEC
  • Up to 6 star goto asisted polar aligment correction.
  • Automatic refraction rate compensation.
  • Custom park and home positions.
  • Integrated Bluetooth and WiFi server/command channel.
  • Refraction rate compensation
  • Automatic meridian flip, meridian flip pause at home.
  • Custom backslash setting.
  • Up to 600x slew rate.
  • Custom limits (overhead, horizon, meridian)
  • Custom observing sites.
  • Large object database: Solar System, Messier, NGC/IC, Herschel, Bright Stars, User Custom Catalog.
  • Manual speed/guide speed rates: 0,5x, 1x, 2x, 8x, 24x, 48x, 300x
  • Slew Rate: Adjustable 150 to 600x
  • Tracking: Sidereal, Lunar, Solar, Fine Adjust
  • Power source: 2A 12VDC (up to 400x) for 600x slew rate use 18VDC (recomended). Max 24VDC. 
  • Tracking resolution, in arc-sec:  0,035
  • Guide resolution, in arc-sec:  0,56 


Installation is as easy as this example for Bresser Exos II, other EQ5 mounts are similar, they share the same motor hardware design;


Download OnStep app from google play.

Manually move your mount axis to the home position (pointing to the celestial north), OnStep asume to be in this position every time is powered on.

Connect motor cables and power on the drive, the motors will not be energized until a “move axis” command is sent.

Disable your device mobile data, connect your android device to “OnStep” SSID, default password is: “password”, configure onstep app to connect to IP address and port: (top right drop down menu --> Connection).

Once a sucessful conection is done go to top right drop down menu --> Observing sites --> Enter you location and UTCoffset --> upload:  This settings will be stored into memory for the actual and next sesions.

Go to main screen, press “Initialize/Park” --> “Set Date/Time”: The drive will take your device date and time, this step need to be done on every power on.

On main screen press “Tracking” --> “Start”: Tracking will start at sidereal rate.

Again to main screen, press “Solar System”: Select  an object and press “GOTO”: The mount will point to the desired object at default slew rate (1,2º/s), default slew rate can be set anytime  from 0,6 to 2,5º/s.

The connection  may be done also throught bluetooth (previously paired with OnStep and configured in the app)

The drive can also be controlled throught any webbrowser, just connect to OnStep SSID and type ""

For SkySafari app control use IP and port 9999

For Stellarium Mobile use IP and port 9998


-This firmware is only valid for Instein ESP32 goto kit drives purchased from september 6 2020 

-Instein goto kit drives purchased from september 6 2020 to september 20 2021 has TMC5160 stepper drivers installed, if nothing else   specified.

-Instein goto kit drives purchased from september 20 2021 and onwards has TMC2130 stepper drivers installed, if nothing else   specified.

This is source code for arduino, contains main drive MCU, wifi, hand control and ethernet adapter firmwares, unpack to anywhere on your PC and follow file instructions.



OnStep-PDF (preliminary)

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EQ5 - Bresser Exos II OnStep Goto Kit

  • Brands Instein Astro
  • Product Code:EQ5 GoTo Kit
  • Availability:In Stock
  • 360.00€