3d Printing on Hill's Space

Pifinder: complete!

hillexed@email.com (hillexed) — Sat, 09 Dec 2023 20:13:06 +0000

I’m building the Sliced PiFinder, a device to help my telescope find things! Previously, I tried using a cheaper IMU but gave up and bought a $30 fancy chip.

Originally I didn’t want to buy a $50 GPS USB stick but the PiFinder creator found a $10 solderable GPS unit for a v2, so I bought one and soldered it in.

After soldering in the GPS chip, dubiously electrical taping it in place, dropping it and cracking my 3D printed parts, printing new parts, using a soldering iron to remove heat inserts out of the old parts so I can place them into the new parts, printing the case, discovering the case wasn’t designed for my battery and blocks access to the on/off switch and USB ports, melting holes in case with soldering iron, putting on a cover plate over the screen and LEDs… I finally put it on my telescope!

PIFINDER: COMPLETE!

Testing on the telescope went well. The printed dovetail mount was slightly too thin and sagged slightly under gravity, but the field of view was wide enough it wasn’t a problem. And even when I couldn’t see any stars through my finderscope, the pifinder’s camera still got a lock.

Eventually I tried using the find-objects feature, and it successfully pointed me towards M31! I tried pifinding to M33, but I didn’t see it by eye. Maybe the streetlight 30 feet away was just too bright? Perhaps it’ll show up on a long exposure phone cam.

Total cost, including the pi and battery pack I scavenged for free: $118. Much better than $550!

Pifinder is almost pifinding!

hillexed@email.com (hillexed) — Sun, 26 Nov 2023 01:17:31 +0000

The pifinder is a tool to help you aim a telescope. It uses a camera to take pictures of the sky, connected to a raspberry pi which uses a database of stars to tell you where in the sky your telescope is pointing. Then, if you want to find a specific object, it tells you what direction to move your telescope in.

I’m building a janky pifinder with some nonstandard parts: instead of a $60 raspi 4 and $50 HQ camera and $25 lens and $30 IMU, I’m using a $10 lens, a secondhand raspi 3, and a cheap “pi camera module v1” from 2013 that was attached to the raspi, and a $20 IMU with unpronounceable name I found lying around in a drawer of sensors. Previously, it didn’t see any stars, so I bought a better camera, an IMX462.

Turns out the two cameras are different sizes, so the enclosure for my first camera didn’t fit the second one. The IMX462 has some holes in it that fit M2 screws, but my local hardware store only sells metric screws in specific lengths like 12mm, while the pifinder wants 8mm screws.

So I designed a 3D printed enclosure for the new camera, and printed it in orange! It was too big; the screws I bought weren’t long enough.

So I designed another 3D printed enclosure for the new camera, and printed it in blue! It did fit!

Then I put it together, and took it outside… and the display showed that the camera is successfully seeing stars! This camera is definitely much better and more sensitive than the old one. Plus, because it’s connected to a raspberry pi, I can just SSH in and ask it to take pictures to see the raw camera output.

The pifinder still isn’t plate solving properly - it should be trying to compute where in the sky it’s looking and it isn’t. It could be the lens/camera combo means this image is a different FoV than it expects, meaning it’s seeing more or less of the sky and the stars are closer or farther apart than it expects. We’ll see.

Maybe this camera will make the pifinder see stars

hillexed@email.com (hillexed) — Thu, 23 Nov 2023 17:42:35 +0000

Pifinder update: the new $33 camera arrived! But it’s slightly bigger than my previous camera, so I had to design a new part to hold it. While the pifinder was designed with M2.5 screws, this camera only accepts smaller M2 screws. I had to go to the hardware store yet again.

The pifinder is designed for a raspberry pi HQ camera ($50). Originally instead I wanted to use a pi camera module V1 ($10, from 2013) because I recycled it from another project, but it didn’t work too well. I designed a custom printed mount for that. This innomaker IMX462 camera is $33 and has a big pixel size, which means it’s more sensitive to light (good for astronomy!). This means I’m on round 2 of designing custom holders for cameras the pifinder wasn’t designed for!

Adjusting for mirror size

hillexed@email.com (hillexed) — Mon, 23 Oct 2023 14:55:28 +0000

I got a mirror that’s 2.3 inches wide. However, several weeks ago, I printed a mirror holder that was designed to fit a mirror 2.46 inches wide. Sure, I could just use the bigger holder, but the bigger the secondary holder the more light it blocks from reaching your mirror. Is it worth a smaller secondary mirror holder that will block half a square inch less light? Yes, I decided. So I opened up the model and slightly scaled it down. It was a bit tricky because I didn’t want to scale down the nut and screw holes, but I counted the sizes and scaled down the outside vertices in blender. I feel bad about wasting my previous print, but plastic is so cheap I’ll only feel a little bad about it.

Printing for the 8\" telescope has begun

hillexed@email.com (hillexed) — Sun, 01 Oct 2023 20:51:59 +0000

I’m not the first person to build a Hadley 3D printed telescope and then want something bigger. There are two 3D printed 8" telescope designs: the “Bradley” is only available by DMing someone on a discord server, and it’s designed for a printer big enough to fit an 8" circle. I don’t have a printer that big! Thankfully, there’s also the “Leavitt”, a design which splits 8" circles into three pieces so they can fit on a normal Ender-sized printer.

I’ve begun printing all the pieces! It’s a lot of printing; at least 100 print hours. I bought one roll of blue and one roll of black filament. In a telescope, you want to make inside surfaces black so they don’t reflect stray light and brighten the view. The tube parts are so tall and thick, and there’s so many near the path of light, that I used up all my black filament halfway through all the tube sections. I’ll need to print the rest in blue but spray paint them black.

Interestingly, there’s also a remix called the Leavitt Lite which edits the Leavitt to use metric screws/bolts and makes many parts thinner and lighter. One interesting change the Lite made is using a bigger secondary mirror than the original for better illumination; I’ve downloaded the file from the Leavitt Lite and edited it to use #10 nuts so I can use that change too. Now I need to find or buy a 62.5mm secondary mirror.

One other thing to think about: metal rods. I have three 36in thin-walled rods in my wobbly first mount. I could reuse those for my Leavitt for free. My donated mirror’s focal length is 43in right now, meaning I’d need to place the eyepiece 43in away from the mirror, and that won’t fit on those 36in rods.

One option is I could grind the mirror and reduce the focal length to 36in, giving me an 8" f/4.5 mirror, and then use my existing rods. Same focal length means same magnification… but I like the idea of having a longer focal length and therefore more magnification than my previous telescope. Another option: I could either leave the focal length alone (or increase it), but then I’d need to buy 3 new longer 1/2" tubes for an extra $40 or so.

Paint, rods, and secondary mirrors. Many things to think about.

Printing for the 8\" telescope has begun

hillexed@email.com (hillexed) — Sun, 01 Oct 2023 20:51:59 +0000

Paint, rods, and secondary mirrors. Many things to think about.

Dumb telescope idea: liquid mirrors

hillexed@email.com (hillexed) — Mon, 18 Sep 2023 17:27:56 +0000

I’ve been thinking about https://www.space.com/liquid-telescope-construction-in-space-ax-1 . I wonder if you could take a circular baking tray, spin it on a pottery wheel, and then pour SLA 3D printing resin into it so the resin would form a liquid mirror, then shine UV light on it to cure it and make a telescope mirror

Attacking vibration in Hill Mount v3

hillexed@email.com (hillexed) — Tue, 22 Aug 2023 16:56:49 +0000

Telescope mount v3 is pretty good, but it still wobbles slightly. If I touch or move the telescope, it wobbles a bit before settling down in 2-3 seconds. Before it settles down, Saturn turns into two images of Saturn next to each other.

I can use that picture and do the math to see how much it's wobbling:

https://www.timeanddate.com/astronomy/planets/distance says Saturn is 18.96" right now. That's a second of arc, 1/60 of a minute of arc, which is 1/60 of a degree. That means it wobbles 2 saturns * 18.96 arcseconds/saturn * 1/60 * 1/60 * 2π/360 radians/arcsecond = .0001838 radians. My telescope is about 1.75 feet long from the center point, so since sin θ = o/h, the tip of the telescope is moving side-to-side a distance of h * sin θ ≈ 1.5ft * .00009192 = 0.08403 mm in that picture. Wow, that's about one printed layer line.

How do I stop that?

Right now my telescope mount looks like this. It has a C-shaped top, so the telescope can rotate in and out.

It’s not a full truss - I can’t put a bar between the two tips of the C because that’s where the telescope goes. As a result, the tips of the C are only supported at one side, so they can move in and outwards. Experimentally, if I put pressure on the top part I can make the top part shift slightly in the xy plane.

I tried designing a tiny truss add-on to the front to help resist sideways force for mount v2:

I tried remaking it for mount v3! This time, here’s what mount v3 looks like. The rectangle in the center marks the telescope Bonk Zone, where I can’t put anything without hitting the telescope.

I printed it out, put it together, and noticed it was a very tight fit. Looks like I forgot to add tolerance to the hole sizes. I tried forcing it in anyways to see if it would work, and…

oh well. let’s see if it works once I reprint with bigger holes.

Telescope mount v3: Complete!

hillexed@email.com (hillexed) — Sat, 29 Jul 2023 01:19:05 +0000

This mount is my stiffest one yet!

Changes from last time:

uses steel EMT instead of wooden dowels, for extra stiffness
flat sides so you can see the degree markings
deeper and more visible degree markings

It feels pretty darn stiff! Unfortunately, tapping the side still makes the telescope wobble. It’s definitely much less wobble than before, though. Maybe it’ll be enough for clear pictures!

Telescope mount v3 is printing!

hillexed@email.com (hillexed) — Wed, 26 Jul 2023 18:47:58 +0000

comment “safe printing mx mount” to lend it your energy

Telescope mount v2: complete!

hillexed@email.com (hillexed) — Wed, 05 Jul 2023 21:50:20 +0000

It didn’t work. The main type of wiggling I was trying to stop is the top part twisting around the z axis compared to the bottom part. This new mount stood up well, but if I placed the telescope on the mount and gave it a sideways nudge, the telescope would wiggle from side to side at a period of about 1/4 s. It does seem less wobbly than my previous square mount, but it’s still pretty wobbly.

On the plus side, I added little degree markers so you could see what elevation your telescope is pointed at. I like them.

I’m stuck as to where to go from here. How do I change this design to make it more rigid? I’m out of ideas. Maybe the wooden dowels are too flexible and I need to buy aluminum rods? But I can’t cut aluminum to the right size. Damping exists as a theoretical idea, but how do I add some in practice?

Telescope mount V2 construction begins!

hillexed@email.com (hillexed) — Wed, 05 Jul 2023 17:22:59 +0000

Starting to build telescope mount v2! I’m using 0.5in rods, and v1 had holes 0.52in wide. This one has holes 0.51in wide, and that was a mistake, it made getting the rods in there so much more annoying.

Triforce of Space

hillexed@email.com (hillexed) — Tue, 04 Jul 2023 01:55:19 +0000

Telescope mount v2 has 3/4 pieces printed! The pretty colors are because I ran out of filament twice

Designing a new mount

hillexed@email.com (hillexed) — Sun, 25 Jun 2023 20:53:32 +0000

My 3D printed telescope has a problem: it’s very wobbly. That means it’s hard to point the telescope at a planet and have it stay pointed at the planet. It also means I can’t focus it well, or take good pictures through my phone.

The telescope itself is fine, but the mount is the problem. There’s a 3D printed mount included in the files with the telescope, and I built that 3D printed mount (after trial and error and discovering pipe sizes are a lie ). However, the creator of the telescope doesn’t actually use the 3D printed mount - he has a mount made of solid wood. I don’t have a wood saw, so I can’t build that.

There’s another mount named Marci’s Mount, made by Marci, which involves using a vinyl record as a turntable so you can rotate the telescope along azimuth (very cool). It uses a sort of truss design with cross-braces to be even more stable, but you need a drill and a saw to use the turntable part. I don’t have either, which is a shame because it seems like a very cool mount.

I decided to try making my own mount. Halfway through studying that one, I discovered a third mount which is very clever and uses more rods to make a truss shape for extra stability. It also uses a clever screws-squeeze-the-plastic design to have more surface area grabbing the rods for more friction.

My plan now is to make my own mount, copying Ivan’s truss design but increasing the size of the bottom part for added stability. Hopefully that’ll make a more stable telescope!