Rack and Pinion Telescope Focuser 1.25-2"

thingiverse

I had a budget-friendly 10" dobsonian telescope that needed a new eyepiece focuser, so I decided to design a 1.25 to 2" rack and pinion mechanism myself. I printed out the parts using ABS plastic and had to do some extensive sanding to make them fit as snugly as possible to prevent slippage from occurring. Since I already had a gear, gear rack, and rod on hand, I didn't need to print those parts, but it's likely that you could get away with printing them if needed. This rack and pinion design has been working well for me on my telescope, though I have encountered some issues with the plastic shrinking in cold weather, making it difficult to insert or remove eyepieces. For the screws, I used M3 screws and purchased brass inserts that I melted into the parts where the holes are located. Additionally, I added a doubled-up strip of aluminum from a soda can along the length of the main tube for the screw to press against, holding it securely in place. To make the print process easier, I had the top of the gear box printed separately so that the hole wouldn't need to be filled with infill material. I also printed the curved part that meets the 10" dob curvature separately to eliminate the need for supports underneath, and then glued the curved base to the base tube using superglue. You can still print out the entire base in one piece if you prefer. The 1.25 inch adapter does not have a threaded end for filters. This is still a work-in-progress project, and I'll be sure to keep you updated on any changes or improvements I make.