CGE Pro DIY OnStep Conversion Kit


This kit is for those people that want to build their own OnStep computer.  It is everything you need to install Nema17 stepper motors directly onto your CGE Pro mount. No modifications to your mount! Just take your OE motors and motor boxes off and bolt these parts on.  The motor boxes will be the latest design with improved clutch knob clearance and threaded inserts for lid attachment.


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This kit is for those people that want to build their own OnStep computer.  This kit comes with everything you need to convert the CGE Pro mechanically to stepper motors.  The wiring hole on these motor boxes are made to accept the CGE Pro connector that is on the OE motor box.

  1. Two – Nema17 2amp 200steps per revolution motors
  2. Two – Machined Aluminum motor mount adapters
  3. Two – 3D Printed PETG motor boxes ( newest design )
  4. Two – 60T GT2 gears
  5. Two – 12T GT2 gears
  6. Two – 200mm GT2 Gates belts
  7. All the stainless hardware you need to attached to the CGE Pro

I have not found a way to leave the CGE Pro motor mount brackets on the mount to put the 60T gear on the end of the worm gear.  So I will include the Celestron instructions on Adjusting CGE Pro Mount Motor Brackets .

Here is the OnStep excel sheet used to calculate the steps per degree.

GR1 is 5 (5:1 gear reduction for 12T – 60T gears)
GR2 is 255 (there are 255 teeth on the RA and DEC CGE Pro worm gear)

For the electronics to control these motors I now offer a kit for that.  It is the CGE Pro MiniESP3 Electronics Package.

60T pulley installation notes

Bracket and motor installation

Video of my first successful movements.

Additional information

Weight 4 lbs
Dimensions 8 × 8 × 5 in


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