CNC-Telescope With Semi-Nasmyth Mount

CNC telescope, semi-Nasmyth mount

[GregO29] had a 10″ GoTo telescope but at 70lbs, it wasn’t really portable. And so he did what any self-respecting CNC enthusiast would do, he put his CNC skills to work to make an 8″ Newtonian reflector, semi-Nasmyth mount telescope of his own design. It also gave him a chance to try out his new Chinese 6040 router/engraver with 800W water-cooled spindle.

What’s all that fancy terminology, you say? “Newtonian reflector” simply means that there’s a large concave mirror at one end that reflects a correspondingly large amount of light from the sky to a smaller mirror which then reflects it toward your eye, preferably along with some means of focusing that light. “Semi-Nasmyth mount” means that the whole thing pivots around the eyepiece so that you can keep your head relatively still (the “semi” is because the eyepiece can also be pivoted, in which case you would have to move your head a bit).

We really like the mechanism he came up with for rotating the telescope in the vertical plane. Look closely at the photo and you’ll see that the telescope is mounted to a pie-shaped piece of wood. The curved outer circumference of that pie-shape has gear teeth on it which he routed out. The mechanism that moves these teeth is a worm screw made from a 1″ spring found at the hardware store that’s on a 3/4″ dowel. Turn the worm screw’s crank and the telescope rotates.

Cutting the telescope mount using the 6040 router/engraver
Cutting the telescope mount using the 6040 router/engraver

All the holes in the wood were CNCed out to make it lighter, but also give it a steampunk feel. In true amateur astronomer style, when you look down on all the holes in the two base plates, they depict all the phases of the moon. But for practical purposes, the smaller holes are sized just right for holding his various eyepieces. He mentions that three of the pieces were too big for his router. As the photo here shows, he solved this by cutting half, rotating the work piece by 180 degrees and then cutting the other half.

Hopefully this whets your stargazing appetite. Alternatively you can do what this star tracking telescope project is doing, which is to convert a manual telescope to a motorized one and sending it GOTO commands. If you want to record the images from your telescope you can do it for just 55 cents. [Xobmo] made a mount for attaching his iPhone. Either way, the sky is not the limit.

9 thoughts on “CNC-Telescope With Semi-Nasmyth Mount

  1. Beautiful and artistic… True. There was a lot of skill that went into building this.

    But as someone with a lifetime experience in building and using telescopes? It looks like a PITA to use. Telescopes are a device in which simplicity and stability are everything. I would much rather have simple teflon on ebony star bearings in place of screws. The very short focal length is another issue, coma is going to be a real problem.

    1. “teflon on ebony star bearings” sounds like something I’d have a helluva time making at home. Props to [GregO29] for solving a problem using his own hands and tools. I think there’s a lot to be said for being able to make a variety of “good enough” things yourself.

      *leans back in crappy chair he knocked together in an afternoon out of scraps* Nice things are nice, absolutely, but kludging is a skill I personally put quite a lot of value on!

      That said: As someone with “a lifetime experience in building and using telescopes”, what suggestions would you make to [GregO29] to refine his design, while maintaining the DIY ethos and limited resources?

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