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Celestron Focus Motor for SCT and EdgeHD Optical Tubes

In January 2019, Celestron introduced a focus motor (Celestron part number 94155) for SCT and EdgeHD optical tubes.  In October 2019 they introduced an updated model ((Celestron part number 94155-A) which addressed an incompatibility with the 9.25" EdgeHD optical tube.  The focuser attaches directly to the focus knob to provide electronic control of all focusing.  The focuser is powered any of three ways:
  • by connecting to any AUX port on a Celestron computerized mount
  • by connecting to the USB port on a laptop or desktop computer
  • by connecting to a 12VDC power source

There are currently four ways to control the focuser:

  • using a NexStar+ or StarSense hand control (update to the latest  firmware to add the new focusing options to the Menu)
  • using any Microsoft Windows-based focusing software compatible with ASCOM (there is an ASCOM driver available for download at Celestron's website)
  • using Celestron's CPWI remote control software in place of the hand control
  • using a small Microsoft Windows-based focusing utility available for download at Celestron's website

For mounts requiring an additional Aux port, Celestron sells an Aux Port Splitter (part number 93919).  Note that for the Advanced Series with GoTo mount, a special splitter is required: part number 93923.

See Celestron's website ( for more details including compatible optical tubes.  Notably, all EdgeHD optical tubes are compatible (note that the focusers made before Oct 2019 - part number 94155 - are not compatible with the 9.25" EdgeHD) , but not all SCTs.  It is not compatible with any 5 inch SCTs.  It is only compatible with 6 - 14 inch SCTs manufactured since the year 2006.  If you are unsure when your SCTs was manufactured, one clue seems to be the sculpted rear cell of the optical tube - the newer models have a raised triangular-shaped portion with rounded corners as seen in the picture to the left.  Additionally, you should download the manual from their website as it details some accessories, particularly for the 6" SCT, that are NOT physically compatible with the focus motor.

Final note, at least one EdgeHD owner found that after installation, the focus motor was unable to rotate the focuser shaft/knob.  The problem was that the screws used to secure the orange mounting ring had heads which protruded above the surface of the orange ring.  Apparently the factory used slightly larger-headed screws on his optical tube.  Celestron should be able to provide replacement screws if this is a problem with your scope, or you can find replacements at your local hardware store.  Be sure they are the same shaft length and are high-quality stainless steel.


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Michael Swanson
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