Motorizing on Hill's Space

My gearbox finally has gears in it

hillexed@email.com (hillexed) — Sun, 14 Jan 2024 23:09:28 +0000

This is going to turn the turntable that my telescope will sit on

Gearbox has some decent progress

hillexed@email.com (hillexed) — Sat, 13 Jan 2024 05:54:02 +0000

I’ll print out a prototype and see if it holds everything the way I want it to.

Question I still need to answer: how do I stop the axles from fall out

Gearbox design going... okay

hillexed@email.com (hillexed) — Fri, 12 Jan 2024 23:19:36 +0000

I don’t know how to design a sketch in one document (for say a stepper motor mount plate) then import it into a different document in a different location (for, say, mounting that stepper in a different place)

First gearbox test

hillexed@email.com (hillexed) — Fri, 12 Jan 2024 19:00:14 +0000

Looks like the belts and pulleys I got fit! Now to design the gearbox and 3D print it so my telescope can move very small amounts accurately

The Jan 2024 Telescope Shenanigan List

hillexed@email.com (hillexed) — Thu, 04 Jan 2024 19:18:07 +0000

I have many projects in mind for telescope upgrades. Since the last list I’ve completed one and added one. Here’s what I want to do this year telescope wise:

#1: Sliced Pifinder (complete!)

Complete! I built a Pifinder for 1/5 of the list price by using a different cheaper camera, secondhand older pi and battery pack, and printing and soldering parts myself. It’s been very helpful when it works, and let me take pictures of M33 even without seeing it! It’s crazy that I have a computer on my telescope at all times.

#2: Motorizing

The Earth’s rotation is my enemy. The stars smear into lines if I take long exposures, where long means “one second”. To fix that, I want motors to move my telescope as the sky moves!

I scrounged some free stepper motors, and bought $40 of gears and axles and bearings from China. One person in the discord for Hadley 3D printed telescopes has already motorized a Hadley, so I’m stealing their overall design: two axes, alt/az, each with GT2 belts and pulleys to gear down the motor for very small rotations, held in place by 3D printed housing and using ball bearings to hold the axes. Unlike that one, which uses 8mm and 5mm axles, I’m using only 5mm axles to make ordering simpler.

There’s lots of work to do, including actually designing the thing. I still need to design the gearboxes, buy wood for the central turntable, and figure out how they’ll fit on it and spin the scope. But if it works it’ll boost the exposures I can take up to ten seconds or so!

#3: Make Bigger Scope

@BeasMeeply donated me an 8" glass blank that was partially ground, and this year I’m going to finish polishing it and make a telescope! I’ve printed all the parts for a “Leavitt”, the only 8" printed scope whose design is public. I’ve confirmed the blank is going to make an 8" f/5.5. I’ve inspected it to figure out it was ready for polishing, poured dental stone, and nearly finished a pitch lap. Now I just need to build a ronchi testing setup and start polishing.

#3.5: meniscus mirrors

Meniscus mirrors are a way to build very big mirrors that are thin so they cool down fast and aren’t heavy. I got a chipped glass countertop for $20 but need to find a way to cut a circle out of it. I also tried making a precision shaped heat resistant mold by pouring refractory plaster into some CNCed wood, but it cracked and failed. I need to try a different way. Once I have my circle of glass and a precision mold, I can put my mirror in a local kiln to shape it, and then grind it into a 12" or 13" mirror. Then, of course, I have to build a telescope around it!

Grabbing Gears

hillexed@email.com (hillexed) — Tue, 12 Dec 2023 19:22:32 +0000

I found a design by d.revan to motorize a telescope using GT2 timing belts and it’s cool. He uses:

GT2 belts and pulleys instead of gears
608-2RS skateboard bearings to let the shafts spin (smart!)
a giant mega printed gear attached to wood for the final gear stage
4:1, 4:1, then 15:1 gear stages

…but I tried seeing how much the parts would be on AliExpress, and it was surprisingly hard to find gears with the right 8mm bore and wider than normal 10mm belt width. And the shipping added up - you’d see a $1 part plus $4 shipping. And buying two different parts from the same seller was twice the shipping! Just the tiny metal rods were $3 with $15 shipping, let alone gears!

So instead I asked around the synthesizer community, and found robotdigg.com, which is a janky 3D printer china company with a slightly hanky website but sells GT2 belts and pulleys for very cheap. And thankfully it all ships from one place, so only one shipping fee! I was able to buy the parts for one gearbox for $25!!!

So $50 later, I bought enough for two gearboxes, one per axle.

Now to CAD it up! D.revan’s design is slightly different from mine because I’m using smaller pulleys, but the idea seems similar enough that I think it’ll work. If I can motorize my telescope for $50 that’ll be incredible.