Almost Forgot – 1.25″ Eyepiece Adapter

Ok, this isn’t strictly a case of “forgetting” to design somethign–I’d planned to just buy 2″ to 1.25″ eyepiece adapters ready-made. But since I’m becoming more comfortable with rolling my own parts, I thought let’s design it and see how much it costs to print. Turns out these will cost less than $8 to print. The heat-set threaded insert and set screw will cost less than a dollar, making the whole thing less than $9.

It is a low-profile design, so it only adds a few millimeters to the eyepiece height. The retention screw is aligned both vertically and longitudinally with the other thumb screws. So the adapter thumb screw will always be the one in the middle. If you have ever unscrewed the wrong screw in the dark because you couldn’t remember which was holding the eyepiece and which were holding the adapter, you know why this is a big deal–especially on a scope with two eyepieces.

The adapter will fit the focuser aesthetically, having the same dimensions and surface finish. It’ll be incredibly light weight. (Even the screw is glass-filled nylon. Seriously, why are people still building telescopes entirely out of metal? Is there an actual benefit or is it just because of the perceived value of plastic?)

Usability win, aesthetic win, lightweight win, cost win.

The part is shown here in gray for clarity, though it will be Onyx black to match the other parts. Or maybe I should have them painted magenta?

Also, I decided to keep the focuser detachable from the tertiary assembly. This way, I can compare different focuser designs easily. This also makes assembling and adjusting the drive plate much easier because it can be done while the focuser is detached rather than the bottom screw being buried in the tertiary assembly. So screw holes for attaching the focuser have been added. Good thing I bought a new soldering iron because there are… let’s count… eight heat-set threaded inserts in the focuser alone.

Here’s a wireframe of the whole tertiary assembly… lol, how did people do this before computers?

With these updates, another batch of focuser parts has been sent off for printing. I will be comfortable calling this focuser v0.5, as it should be fully-functional and ready for “alpha testing”.

Also, the first filter cartridge print is on the same order. Turns out the threads on an M48x0.75 filter are still way, way too fine for 3D printing. This is unfortunate since it’s another part that could have been incredibly cheap to make. (The part costs a few bucks to print, but the aluminum thread adapter I’m gluing in retails for $20. Will have to find a better source for these.)

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