One of the things I did not like about my Celestron Nexstar 8 SE was the focuser. Trying to focus on a planet was a pain. The image jumped all over the place due to how the mount holds the telescope. Any slight movement caused the image to jump. I wanted to solve this by adding a focus motor.
The Celestron Focus Motor lets me control the focus from the mounts hand control or computer via USB. It adjusts the focus without causing the image the jump around! Installation is straightforward. You only need to remove the existing focus knob, replace a plate, and secure the motor. Here are the steps I took to install the focus motor on my Nexstar 8 SE.
Step 1: Unbox the focus motor
The package includes everything you need to install on a 6″ – 14″ Celestron SCT or EDGEHD. You’ll need an additional retrofit kit for the RASA 11. There are two supplied cover plates, the one with an edge cut off is for 6″ through 9.25″ models. The other is for 11″ & 14″ models.
Step 2: Remove the existing focus knob
Remove the existing rubber focus knob. I was able to pull mine off by grabbing the end and slowly wiggling the knob out. The instructions say to use a flat head screwdriver to pry off the rubber knob if you cannot “simply pull it off.” Store the rubber knob in a safe location.
Step 3: Remove the existing cover plate
Use the supplied screwdriver to remove the three screws from the existing cover plate. Save these screws since you’ll need them to install the new cover plate. Carefully remove the cover plate and set it aside.
Step 4: Determine which cover plate to use
For 6″ – 9.25″ models, use the top cover plate, for 11″ & 14″ use the bottom plate. If you are lucky enough to own a RASA 11, you’ll need to purchase an additional retrofit kit.
Step 5: Install the new cover plate
Use the screws you removed from the existing cover plate to install the new plate. Note that the orientation matters. For 6″ & 7″ models install the plate with the cutout facing away from the telescope. For 8″ & 9.25″ models the cutout should face towards the telescope.
Step 6: Prepare motor
Make sure the white arrow is pointing within the white range marking on the motor coupling. If it is not, use the supplied wrench to rotate the motor coupling.
Step 7: Loosen the clamping screw
Use the supplied hex key to loosen the clamping screw.
Step 8: Install adapter sleeve (6″ – 9.25″ models only)
Align the sleeve with the clamping collar. Use the supplied screw to secure the sleeve into place.
Step 9: Install set screw (6″ – 9.25″ models only)
Use the supplied hex key to install the set screw into the clamping collar. Do not tighten the screw yet.
Step 10: Determine focus motor placement
Place the focus motor on the brass focus tube and determine where to point the motor housing. The position is entirely up to you and depends on your use case. I decided to point the motor housing to the right side since that allows me to point the telescope at the zenith without the motor housing hitting the mount. It also won’t get in the way while viewing objects since I tend to stand to the left of the telescope.
Step 11: Install focus motor
Use the supplied hex key on the two captive screws to attach the motor to the plate. Alternate between both screws until fully secured.
Step 12: Tighten set screw (6″ – 9.25″ models only)
Tighten the set screw from step 9 with the supplied hex key.
Step 13: Tighten clamping screw
Use the supplied hex key to tighten the clamping screw.
Step 14: Test via the hand controller
Connect the AUX port on the focus motor to the AUX port on the mount and turn on the mount. Open the menu and navigate to the Focuser option. Choose the Calibrate option and wait until the calibration finishes. This video shows what it should look like:
You’ll need to use the Celestron Firmware Manager to install a newer firmware if you don’t see the Focuser option in your hand controller.
Step 15: Use it!
You should now be able to control the focus from your hand controller. You can also control via ASCOM or download the Celestron Focuser Utility Program on Windows.
A focus motor is a worthwhile upgrade. It is a lot easier to obtain a good focus, especially if using a tool like SharpCap, which has a focus assistant. Both my rigs now have a focus motor. My deep space object rig has a Pegasus Astro FocusCube 2.