A few years back, I sold my beloved 12" Zhumell Dobsonian in favor of the venerable 12" Portaball. Before moving on, I compiled a list of 3D printing improvement ideas tailored for the classic steel OTA (Optical Tube Assembly) Dob.
Pictured above is an example of a conceptual multi-section Dobsonian base ("stool") that was never printed in time. The goal was to create a more portable mount that slides directly over the OTA for easy transport. The ground board was designed using a 3/4" plywood base paired with a 3D-printed raised lip ring rail (split into multiple sections to fit a standard 10x10-inch printing bed as well).
Note on "Files?": I am not publishing STLs or CAD designs at this time, as most of these modifications require precise measurements of your specific scope and iterative fitting in place. However, if there is enough interest, I may share some of my base files down the line, adding to what I have already published here before.
23 easy 3D-Printed Dobsonian Projects & Mods ideas
Peep Sight Pointer: If you prefer observing without an optical finder or don't have one handy, print a simple two-piece peep sight. Attach front and rear components to your OTA using double-sided foam tape after aligning them with your eyepiece view. A longer base distance between the two sights yields higher accuracy. Tip: Print in white PLA for better visibility in the dark.
Custom Cheshire & Sight Tube: Print a tailored Cheshire collimator and sight tube sized to match your focuser and optical specs exactly. A custom fit allows for quick, high-precision mirror and focuser alignment—often outperforming commercial laser collimators. Tip: Use clear or white PETG, as it has low thermal contraction in cold weather and allows side-lighting to make alignment rings stand out.
Magnetic Sliding Counterweight: Solve vertical balance issues when swapping heavy eyepieces or accessories by printing a curved magnetic counterweight block. Embed strong neodymium magnets near the bottom curved to your OTA radius surface (covered by just 0.1–0.2 mm of plastic) and build an airtight box on top to hold lead shot or weights.
Dedicated Smartphone Eyepiece Adapter: Skip generic, flimsy phone clamps. Model a custom single-piece bracket contoured specifically to your favorite wide-field eyepiece and phone model. This creates a rigid, perfectly aligned setup for quick lunar, planetary, or bright DSO snapshots with zero setup hassle.
Solar Aperture Cap & Projection Screen: Print an oversized top lid with an off-axis sub-aperture hole for solar viewing. You can fit this sub-aperture with Baader solar safety film, or build a projection screen frame to view the Sun safely on paper ~1 ft behind the eyepiece (add a 1/4" threaded rod in a plastic enclosure.
Safety Warning: Never operate a 12" scope at full aperture on the Sun. The focused solar energy will quickly destroy eyepiece ND filters, melt plastic focuser parts, and vaporize tube coatings. Always use opaque (black) PETG for solar caps to prevent light bleed, design overlapping light-seal seams, and ensure all assembly glue is completely cured before use to avoid off-gassing onto mirror coatings.
Bottom Dust Cover & Mirror Shield: Print a removable cover for the lower end of the optical tube. This protects the primary mirror, mirror cell, collimation hardware, and cooling fan from dust kicked up while walking around the scope in the dark, as well as keeping insects out.
Adjustable Observing Chair Components: Build a custom height-adjustable observing seat using timber or metal tubing paired with sturdy 3D-printed joints and latching mechanisms. Tip: Print structural parts in ABS or ASA for higher impact resistance and mechanical strength.
TPU Eye Guards: Use flexible TPU filament to print custom eye guards for your eyepieces. You can design integrated side-flaps to block ambient light pollution (especially helpful when wearing glasses) or scale smaller eye-sockets comfortable for young children.
Dedicated Push-Pull Handle: Print an ergonomic (ball shaped) handle and mount it beneath the Upper Tube Assembly (UTA). Enlarged sculptured handles provide finer manual tracking control when following planets and remain comfortable to hold in cold weather compared to bare metal of the OTA.
Mount Rigidity Upgrades: If your mount "stool" flexes or wobbles, print structural corner brackets with screw reinforcement to stiffen the joints. You can also replace central pivot bolts with a wide-diameter bearing ring surface (as mentioned for the title picture).
Note: Remember that a Dobsonian mount is a three-point ground-supported platform, not a fork mount. Avoid "lazy susan" metal ball bearing tracks idea, which add jitter and lack smooth motion control.
Azimuth Setting Circle: Transform your ground board into a navigation tool by 3D printing marked 0°–360° degree sectors. Embed recessed or raised degree ticks in white PLA (to fill with paint later) or use dual-color printing. Saw/drill a view window into the top rotating board with an indicator needle and a nice frame (add a red LED illumination if you wish). You can calculate true Azimuth offset using certain mobile astronomy apps. Add a magnetic base electronic construction inclinometer for the altitude dialing (or 3d print a mounting point "socket" fixture for a non magnetic one). This pointing system might surpass many aftermarket DSC kits for a typical particle board mount these Dobs shipped with.
Damped TPU Mount Feet: Replace stock hard plastic or metal feet with hard TPU pads. High-friction TPU grips the ground better to prevent sliding and actively dampens minor ground vibrations.
Focuser & Eyepiece Dust Caps: Keep dust, ambient moisture, insects, and debris off sensitive optical surfaces by printing custom press-fit caps for all focusers, adapters, and eyepieces. Use TPU.
Equatorial Platform Parts: Print gears, motor mounts, bearing tracks, and sector plates to construct a DIY equatorial platform (EQ platform) for hands-free tracking at high magnification. Just keep in mind that you can't just repeat metal parts in plastic. Specific designg for 3D printed parts use must be researched same as for wooden parts (i.e. add metal rails on top of the plastic surface).
Internal Light Baffles: Instead of messy, shedding flocking paper, print thin internal light baffles sized to match your tube's light cone. Secure them inside the OTA using flexing polyurethane adhesive or print integrated spacer legs to maintain uniform spacing.
Boundary Layer Cooling Fan System: Upgrade your primary mirror cooling by routing fan airflow across the front face of the glass, rather than just cooling the back. Print a low-profile baffle ring above the mirror face and add a fine mesh screen over the fan intake to avoid pulling dirt into the cell. With that you can start observing planets at high mag. not waiting for the complete mirror thermal mass cooling.
Snap-On Dew Shield & Light Baffle: If your scope has a short UTA, print a lightweight extension ring to act as a dew shield and light baffle directly opposite the focuser. Model the interface ring so it slides over the lower OTA for easy storage when not in use being a bit larger than the OTA end rings.
Barlowed Laser Collimator Adapters: The Barlowed laser technique drastically reduces sensitivity to internal laser misalignments while doubling collimation precision. Use any laser pointer with rough alignment rocking socket and a flat or angled screen around the output hole.
Ergonomic Control Knobs & Keys: Print larger, easy-to-grip plastic knobs over existing small hardware or mirror adjustment screws. You can also print removable collimation keys that stay compact during transport but offer precise finger control during alignment.
Helical Focuser: Print a smooth helical focuser if you want precise fine-focusing control or need to convert a 1.25" setup to accept 2" barrels on a budget.
Eyepiece Parfocal Rings: Eliminate constant refocusing between eyepiece swaps by printing custom parfocal stop rings. For large focus offsets, print threaded barrel extenders (ensuring the focuser metal thumbscrews still clamp onto the metal portion of the eyepiece barrel to prevent wear). Not critical if you have a split ring focuser.
Piggyback Camera Mount & Counterweights: Mount a DSLR or mirrorless camera with a telephoto lens parallel to your OTA using a custom-curved tube clamp and tension strap. Balance the added weight on the top using your 3D-printed magnetic counterweight system on the bottom.
Trays, holders: You can surely 3d print a variety of OTA and Base attachments to conveniently hold your eyepieces, smartphone, tablet. Just keep in mind that all of them will change the Dobsonian components weight and balance. Consider adding counterweights and increase PTFE bearings surface for permanent "weight increasers". Even with this ingenious sturdy 3 legged stand design the stickiness of PTFE may ruin the smoothness of telescope operation noticeably.
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