March 25, 2026
Description
A primary mirror cover featuring a 92 mm fan mount for the Sky-Watcher 200p (200 mm) Dobsonian telescope.
Features:
92 mm Fan Mount: Enables fast mirror cooling to ambient temperatures. Designed for use with a USB adapter for fan speed control.
Mirror Protection: Shields the primary mirror from collisions and debris.
Integrated Feet: Transfers the weight of the telescope directly to the steel mirror structure when stored vertically.
No Modification Mounting: Attaches via clamps to the solid metal mirror support; no modifications to the telescope are required.
Collimation: Only four screws need to be removed to access collimation bolts.
Cable Management: Includes a zip-tie point for fan cable strain relief.
High Rigidity: Geometry designed to minimize vibrations.
Ease of Printing: Split into sections.
This design can likely be adapted to other 200 mm telescopes by modifying the clamp design. The CAD files are provided.
Assembly: 16 × M3×8mm screws + M3 nuts.
Electronics: 92 mm 12V fan (ideally, https://www.noctua.at/en/products/nf-a9-pwm and a USB-to-12V adjustable fan controller cable.
Recommended: 92 mm fan grill (3D printed (https://www.printables.com/model/1121336-high-efficiency-noctua-92mm-fan-grill/related) or bought) and fan vibration-dampening mounts (not mandatory if you have a good quality fan).
Fan Mounting: 4 × M3/M4×10mm screws + M3/M4 nuts. If using M3, washers are recommended.
Clamp Mounting: 16 × M3×8mm screws + washers.
Inserts: 16 × M3 heat-set inserts (OD: 5 mm, Length: 3–4 mm). These are the standard wide-profile inserts with the helical knurling.
Cover Assembly: Print the four cover sections and join them using 8-16 M3 screws.
Insert Installation: Using a soldering iron, install the M3 heat-set inserts into the cover at the clamp mounting points. Note: Nuts cannot be used here because the rear of the panel is inaccessible once mounted.
Fan Installation: Secure the fan using M3 or M4 hardware.
Initial Clamp Fitting: Attach the first three clamps to the cover. Keep the screws slightly loose to allow for adjustment.
Final Mounting: Place the cover onto the rear of the telescope and attach the fourth clamp. Tighten all screws until the cover is secure.
To perform collimation or otherwise access the mirror, only repeat Step 5 in reverse (remove the 4 screws of the final clamp). Using the same head type as your collimation screws is recommended for convenience. If frequent access to the mirror is required, two screws is more than enough to hold the clamp.
This cover is designed to (barely) fit on a Voron 0 bed (110×110 mm).
For the cover (×4):
Nozzle: 0.4 mm
Layer height: 0.2 mm
Infill: 20%
Walls/Perimeters: 3
Top/Bottom layers: 3 bottom, 4 top
Bed adhesion: I would recommand a 5 mm brim.
Material: PLA (Geeetech Black PLA)
Print time (VORON 0): ~1h05 per piece
For the clamps (×4):
Nozzle: 0.4 mm
Layer height: 0.2 mm
Infill: 40%
Wall loops/perimeters: 4 or 5 (this is important for the strength of the clamp)
Top/bottom layers: 4 bottom, 4 top
Material: PLA (Geeetech Black PLA)
Print time (VORON 0): ~30m per piece
This design is released under CC-Attribution License.
Other modifications for my Sky-Watcher 200P:
License:
Creative Commons — Attribution
CGrassin
