Here’s the long-awaited update on my 200mm f/3.3 Newtonian build. After many months of design work and assembling the optical tube, the telescope is finally taking shape.
In my last post, I was still debating which design to use for the secondary mirror support. I was torn between the simplicity of a 3D-printed version and the opportunity to hone my machining skills by crafting one from aluminum. In the end, I opted for the aluminum build, machining it from 6061 and 6063 alloys I had on hand. The final result turned out exceptionally well, with tight tolerances that ensure maximum rigidity. The strength of the design exceeded my expectations—I even had to reinforce the steel tube to prevent warping of the OTA or the spider’s attachment bolts from pulling through the mounting holes as I tightened it into place. The final design for reinforcing it is still work-in-progress, but for now some scrap pieces of metal will suffice to distribute the pressure. I also anodized the parts myself, that was a skill that I had to learn from scratch like many others that are needed for completing this kind of a build. After a bit of trial and error I found the right "cook book" for my parts and they turned out quite nicely, especially I like the bright red centerpiece that matches the tube ring on the front.
Despite opting for aluminum for the primary structure, 3D printing proved invaluable for creating parts to securely support the secondary mirror. I tried to avoid any adhesives, which could lead to warping and instead devised the design shown below. It gently holds the mirror in a custom-fitted plastic shell, providing a firm yet distortion-free mount.
For the primary mirror, I repurposed an old aluminum shell and 3D-printed an outer cage to support it. Initially, this design was intended as a prototype, with a final version planned to be machined from aluminum. However, after testing, I haven’t found any flexures or distortions in the mirror support, so it may be more durable than anticipated.
On the topic of flexures, I’m also building a precision collimator specifically for this scope to detect any subtle flexure points that a typical commercial collimation laser might miss due to large spot size and poor attachment to the telescope. The main body, along with all of its components, was turned from 6062 aluminum, and I milled the collimation screw holes on my mini-mill for precision. Of course, collimating the collimator itself presents its own challenge, requiring (drum-roll)... another collimator! The setup I devised helps eliminate variables, ensuring that any tilt introduced by the telescope's focuser won’t impact the laser beam’s accuracy when collimating it on a separate, much more precise rig with essentially no runout as the 3D printed bushing on the top of the collimator can be adjusted for a snug fit of the collimation tool.
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