2 inch helical telescope focuser

thingiverse

Update: Centering the eyepiece on the optical axis has proven challenging with this design. Decreasing the drawtube width adjustability will likely have limited impact (despite printed drawtubes functioning effectively). I've been brainstorming innovative ways to maintain centering, but designing a crayford style focuser might be the better solution. A notable finding is that 1.25-inch eyepieces were accommodated in the design referenced at http://www.thingiverse.com/thing:13476; however, I wanted to accommodate 2.0-2.6 inch drawtubes without using metal bearings or increasing weight. The design may lack aesthetic appeal, and feedback is invited on this aspect. The mounting plate measures .55 inches in thickness and aligns closely with 1/2-inch plywood; although this arrangement might need reassessment to provide sufficient backout for larger eyepieces, necessitating possible adjustments. The printed parts accommodate mounting holes that are somewhat unusual at 3+1/8 inches apart. Experience revealed the carbon fiber rod fits snugly into the printed components, but the plastic wheels still rotate smoothly on the rod; this unexpected result contributed to a helical operation. One imperfection exists: the drawtube can occasionally become slightly misaligned. This issue is somewhat manageable as long as zip ties are employed instead of rubber bands for securing alignment. Notable design specifics revolve around an impending 10-inch F/4.485 telescope with a secondary mirror measuring 2.49 inches in diameter and a tube ID of 12 inches (partially made up of a truss structure). Consequently, the light cone's 75% zone at the scope's front measures approximately 11.598 inches, thus necessitating attention to having an adequately long drawtube. To successfully print these components: Ensure ABS juice is used due to limited surface area. Obtain necessary materials, including a mounting plate, three units of "2inchPetal," and three units of "2inchPetal LHT mirror." Utilize a 1.8 mm Carbon Fiber rod in conjunction with 23/32 inch rubber wheels from a remote-control hobby shop. Aim to secure the rod either through friction welding or using fuel hose for captive installation. Drill the CF rod using a 1.8mm drill bit and the pre-printed holes, along with making suitable holes for attaching the petals via nylon bolts (#6 or #8 size). Ultimately attach the mounting plate to the secondary cage of the truss tube telescope utilizing #10 sized bolts once prints are completed. While the STL files may require adjustments due to an under-calibrated printer within a 0.01-inch tolerance, this could lead to slight differences from expected results, necessitating some experimentation and adaptability in print processes.