Amazing project and write up, very good timing too! I’ve been into amateur astronomy since I was 13, owning a few telescopes and spending many hours with family at star parties.
This week I pulled out our big Meade 10” SCT and our small Meade 4” Newtonian to show my 7yo son the moon and Saturn from my parents Bortle 8 backyard. It was wonderful seeing his awe and surprise, and the fact that my parents were there to see it too.
That 10” SCT is on an old fork mount which is motorized but has no GOTO capabilities at all. I’ve also gone down the rabbit hole of researching mount options, thinking I could just buy my way out of it. However, as much as I like the idea of GOTO, a big part of the fun is finding the objects. So I’ve never been able to pull the trigger. I did buy a ZWO 585MC though, I’ve always wanted a dedicated cooled camera.
That said, we have lost way too many hours to trying to find objects. The Telrad isn’t always enough!
I’ve been looking into using my 3D printer and electronics know-how to build my way out of this. I was even thinking of swapping the motors for NEMA 17 steppers.
Then I stumbled upon PiFinder, and I think this project is going to be the exact balance of automation and Push-to guidance that I would like.
It’s a wonderful hobby and I think the latest in 3D printing and PCB manufacturing does mean we’re going to be able to solve a lot of these problems soon.
waerhert · 8m ago
Thanks! If you hook your ZWO up to Kstars/EKOS you can use plate-solving in software to find out exactly where your scope is pointed at and then adjust accordingly.
fusslo · 2h ago
I've been using freeCAD for about 3 years now. Looking at what he was able to make with it blows my mind. I love freeCAD, but I don't think I've ever been so continuously frustrated by a piece of software
waerhert · 1h ago
Though very grateful for projects like FreeCAD, I did encounter a fair bit of frustration while designing this. Especially random crashes, which only got worse as the project got more complex. As far as usage goes, it's mostly a matter of knowing how to do things in FreeCAD. I haven't encountered anything I could not achieve in FreeCAD. Having no experience in other CAD software probably helped sticking to it.
alnwlsn · 25m ago
I came to FreeCad with some years background in Inventor, NX and SolidWorks. The jump from any of these to FreeCAD is not very big; you're doing a lot of the same things. But, most of the problems FreeCad has are solved in those, so you can sort of do anything in them and be none the wiser. In FreeCAD, you need to think a little bit more on how it's going to do things.
But most people don't learn the big CADs first, they learn Fusion. The few times I've tried Fusion, it's given me a headache. It's probably a bigger headache going the other direction.
Then, there are those who do all their CAD work in OpenSCAD. They scare me.
waerhert · 19m ago
Haha, the thought of using OpenSCAD briefly crossed my mind when I found out about it but I didn't want this project to take a year extra to complete. I do consider exploring some of the other CAD alternatives though if budget permits.
Klaster_1 · 2h ago
For real, I've been using FreeCAD for small hobby stuff for 7 years and still often find extremely frustrating UX issues in features new to me, stuff that wouldn't pass QA (I'm a FE dev and know a thing or two about that). When I proceeded to understand why overconstraints are an error and not a warning, I immediately discovered a multiple page thread on FreeCAD forums with regulars gaslighting how everything was exactly as needed because "performance", despite this being a deliberate choice, not a solver limitation. This gatekeeping attitude is really off-putting, the project needs a UX expert and a good community manager to root out that power user crap.
fidotron · 2h ago
That was the classic GIMP problem too.
Meta comment: damn it's good to see something worthwhile at #1 on HN this morning.
Aurornis · 1h ago
I think it’s great that we have FreeCAD as an option and I’m excited to see it mature.
That said, I recommend Autodesk Fusion free tier for anyone who just wants to get quality work done quickly. Some will refuse to use it on principle and that’s fine for them, but it really is quality software free for hobbyist use with trivial restrictions.
EDIT: Getting downvoted, presumably for suggesting a non-OSS software to get a job done. However I’d recommend anyone who just wants to get work done at least consider the options at their disposal. Not every software decision needs to be made on principle.
nancyminusone · 1h ago
Those who have bought into "free" closed source software simply haven't been burned hot enough by it yet. It might take a while, but you'll learn your lesson one of these days.
Aurornis · 1h ago
Honestly it’s useful enough that I’d pay the several hundred dollars per year if I had to. It’s that much better. The money spent would be well worth it (for me) for all the time saved over using FreeCAD. I’ve used multiple professional CAD packages and I’m just not interested in going back.
People sneer and tell me I’m going to get burned some day, but meanwhile I’ve been using it to great effect for many years for hobby projects that I can share around and edit easily.
consp · 53m ago
I'm not going to agree to any of the "free" (you sign away all rights to the things you made free) tiers. Not that anyone would ever use my things but it's out of principle. FreeCAD has issues but is good enough for most people. And once you want to do really complicated things and also can cope the hundred of euros per years fine, but don't complain other people should do the same because you can.
Aurornis · 32m ago
> (you sign away all rights to the things you made free) tiers.
Do you have a source for this? Or are you speculating?
> but it's out of principle
Great that it works for you. I have limited time for hobbies and I can’t justify making choices based on principle to avoid hypotheticals that even you admit aren’t going to happen.
> but don't complain other people should do the same because you can.
I’m not complaining. Anyone who wants to use a certain software based on principle is free to do so.
I’m sharing recommendations from my own experience and that of my peers. If the goal is to focus on the project you’re trying to do instead of fighting with software then people should be aware of their options.
nancyminusone · 51m ago
Unfortunately, those who (used to) use Autodesk Eagle can't say the same, and they were willing to pay.
eurekin · 1h ago
Can concur. I jump between OnShape and FreeCAD in my free time. OnShape feels very polished. I go back to FreeCAD, because I've bought some models, I don't want to publish in OnShape's free tier.
It's amazing how much can be done, but anything that I think will take an hour, lasts 6. Many times into the night.
imtringued · 2h ago
Three years should be more than enough time to have learned how to perform a few simple extrusions and pockets. What we're looking at here is essentially a pipe with a cap.
Free cad gets really complicated the moment you want to do surface modeling.
zokier · 1h ago
One thing that I'd be interested in is having telescope mount suitable for doing quantitative measurements, basically doing astrometry from first principles. To me solving the orbits of planets (etc) based solely on my own measurements sounds very compelling. It would be like retracing the steps Kepler etc did.
waerhert · 1h ago
Sounds like a really interesting potential project. I've been pondering a system that would make amateur observations usable beyond pretty pictures. Single frames captured could be shared in raw form along with metadata (time, coords, calibration frames), potentially allowing aggregators to process it for scientific research (or even prettier pictures). The Vera C. Rubin Observatory is now able to capture the entire southern hemisphere in a couple of days. Imagine having our capturing software contributing to a planet-wide crowdsourced telescope array.
Finnucane · 39m ago
Kepler did it without a telescope, using Tycho's naked-eye observations.
artgship · 1h ago
I love this so much. Is there any open-source software that calculates where a given planet or star might be (based on your coordinates) and automatically finds the star / planet and then follows it? Can these mounts be used with such software if it exists?
waerhert · 1h ago
Stellarium and Kstars (which has EKOS built in) are both very good planetarium software. Both can interface with indiserver, which can talk to many astronomy devices such as mounts, filter wheels, cameras. I use Kstars mainly for controlling the mount, and Stellarium mainly for finding nice targets.
artgship · 1h ago
Thank you!
krisoft · 1h ago
> Is there any open-source software that calculates where a given planet or star might be (based on your coordinates)
Sure. Skyfield is a python library to calculate that (among others). Right on the front page is an example how to calculate the azimuth and elevation of Mars: https://rhodesmill.org/skyfield/
artgship · 1h ago
Thank you!
ddahlen · 3h ago
This is really impressive! I considered buying a big harmonic drive mount for my scope, but the cost is really prohibitive.
I have experienced the pain of getting ekos/kstars/indi tools to work well on my personal scope. If you want to try driving indi devices via python I have some python code (it's not super polished, but it does enough for my needs): https://github.com/dahlend/contindi
waerhert · 13m ago
Cool project. What prompted you to write this? Asking because EKOS already has pretty good scheduling features (I've seen, not used). Along the way I did vibe-code a TUI for controlling the INDI server running on the MeLE 4C minicomputer attached to the telescope: https://www.svendewaerhert.com/content/blog/telescope-mount/... - I switched to a headless setup using a remote indi server after having a bad experience with reliability using remote desktop in Gnome. I'll probably put this TUI on Github once I clean it up a bit.
stavros · 1h ago
This is great! I never understood how people learn how to make solid PCBs, I've made a few things but I think I must be missing some decoupling capacitors or resistors or whatever, because my microcontrollers aren't very stable. How do you all just know what stuff to put on the PCB? Do you read the datasheet for the component and add whatever is there?
waerhert · 1h ago
Checking the datasheet is essential, they usually show the “must-have” parts around a chip. Beyond that, good habits are adding decoupling caps close to the pins, keeping ground solid, and following the reference layout. I also learned a lot just by listening to experienced designers explain their choices, like here: https://www.youtube.com/watch?v=aVUqaB0IMh4
stavros · 39m ago
Thanks, I'll read more datasheets, as I've kind of just been winging it (with terrible results, as you saw).
Palomides · 1h ago
basically every part will provide a minimal schematic in the datasheet or have a reference design you can copy from
some stuff may be somewhat glossed over, like usage of ground planes or which traces you're supposed to keep short, but when those are important they'll usually be mentioned, or even spelled out in a application note
bongodongobob · 57m ago
Yeah, you have to read the data sheets. Beyond that, use decoupling caps for all power pins, as close to the chip as you can, and make one side of the PCB a ground plane. These 2 things should solve most of your issues.
stavros · 38m ago
Excellent, thank you. I already do the plane, but not the caps. Thanks!
bhouston · 22m ago
You could sell kits for this btw. There would be demand. And I think you could be quite successful.
The reason is that Trump is tariffing the hell out of the main Chinese telescope accessories manufacturer, ZWO. So if you can provide a non-Chinese alternative....
Think of trying to be Prusa 3D solution in the astrophotography area.
donkeybeer · 56m ago
So is the accuracy and stability he achieved better or worse than the commercial mount?
waerhert · 44m ago
Short answer: it's in the same ballpark as other mounts of the same size. The theoretical accuracy for RA is 0.198″ (65,536 steps and 100:1 reduction) and for DEC is 0.253″ (256*200 steps, 100:1). In practice many things will reduce this accuracy: seeing, proper polar alignment, sturdiness of the wedge and tripod all account for some loss in accuracy. My highest achieved accuracy was probably around 1″ during brief moments, I'm sure with excellent seeing this could reach <1″ performance.
donkeybeer · 38m ago
So do you think that complex mechanism ended up no better than the normal mounts? It could be execution too, I am no good at experiments and sometimes even "proven" designs end up a bit subpar, so it could be the design was alright.
waerhert · 31m ago
Not sure what you mean with complex mechanism. The mount has a similar architecture to other commercially available mounts like the HEM15 iPolar for example.
donkeybeer · 46s ago
I am a bit idly curious since I plan to build a telescope sometime. Nothing as complex as this, just a manually guided dobson.
donkeybeer · 2m ago
Oh ok. I didn't know harmonic drives were standard in commercial mounts.
mrgaro · 2h ago
I'm most impressed with being able to order the CNC'ed metal parts. I'm just a novice cad designer and I'd love to learn that capability.
dylan604 · 1h ago
I joined my local Maker's Space specifically for the machine shop. They had a CNC machine that I took the classes on to be certified. I designed my first simple plate design piece for cinema camera support gear in the CAD software they had connected to the machine. There was even a bit of software that generates the G-code with a simulator to check for head crashes. However, every time I went up there to actually try to build the piece the unit was down because someone crashed the head and destroyed bits. Instead, I wound up using the regular metal working machines to hand make the first piece. It ended with square corners instead of rounded, and some of the hole alignment wasn't as precise as intended. I wish I would have known of one of these types of sites to have the piece still CNC'd instead.
4gotunameagain · 2h ago
It's super easy actually ! 1) Upload step file, 2) see what's possible:
Xometry and pcbway are alternatives, among many others
davidhyde · 1h ago
Loved the write up, well done to the author. I get the same feeling building stuff with freecad and then printing it. Feels like there is no limit to what can be done. After going through the growing pains of designing stuff that was just poor and difficult to print I’m now confident enough to send it to be printed by jlcpcb or pcbway. And when they tell me to accept the risk of a failed print then I think, “I feel your pain, good luck”. So far I have never gotten a failed print back. Maybe a little warped but way better than my attempts. If I never have to use my large resin printer ever again I will be happy.
On the pcb front, I dread going through those final steps in the pcb ordering process. No matter how many parts I preorder, there is always something that is unavailable. So much churn in component availability.
dylan604 · 1h ago
After using standard EQ-mounts for so long, seeing something without a counter weight just looks wrong to my neanderthal brain. My current mount weighs 40lbs, the counter weight is 17lbs, and the tripod legs are 20lbs. So that's over 75lbs of weight and size of gear to move around every time it goes on a road trip. This design looks like it was a fraction of that. Color me intrigued
waerhert · 57m ago
I estimate a load capacity of 8-10kg. It's not designed for the really big equipment cause I also would like to take it on camping trips. If I were to do this again I will definitely add a threaded hole to mount a counterweight bar. I've noticed the tracking accuracy drop slightly when the mount is in the most overhanging positions.
dylan604 · 45m ago
It looks like you have a typical OTA attached, what camera are you using with that? I've only ever used my DLSR attached to the OTA for prime photography, but it is heavy. I've learned to test the position by hand of the camera through the full rotation to see how the orientation of the camera will change throughout the night to prevent hanging situations and so it has forward tension. I noticed more backlash type issues when it had reverse tension. The one thing I haven't done yet, is to just attached the camera to a small ball head to do tracked wide angle images. However, I really haven't done any dark sky shooting in many years, pre-Starlink. I wonder if long tracked exposures with wide angles would ever not be affected by Starlink trails
waerhert · 36m ago
I switch between the cheap Byomic 76/700 newton and my Sigma 600mm lens (Canon EF but using an adapter to fit the Olympus body). I tried to get the DSLR looking into the newtonian but it was just too heavy, causing the plastic focuser to simply bend way off axis. I've since bought a dedicated astro camera (Neptune C II) which fits alright on the newtonian. I'm keeping the Byomic 76 only for visual observations now. Looking to buy a proper refractor of around 480mm. The Sigma 600 does alright with the DSLR but isn't very sharp, hard to focus and suffering from some coma. It's good enough to learn the ropes for now.
sn0opy · 52m ago
Just for comparison:
I've got a Juwei-17 (Onstep harmonic drive with performance similar to the ZWO AM5N, but at nearly half the price) paired with the ZWO TC4 carbon fibre tripod.
The tripod has a load capacity of 50 kg (110 lbs) and weighs just 2.5 kg (5.5 lbs). The harmonic drive mount has a load capacity of 13 kg (29 lbs), or 18 kg (lbs) with a counterweight, and weighs 5.5 kg (12 lbs). Alltogether, the setup weighs about 8 kg (18 lbs) since I don't have to use counterweights.
Aaargh20318 · 2h ago
Cool project. Strain wave mounts are fantastic. Just ordered a wave 150i myself. Can’t wait to not having to waste time balancing my scope anymore.
ryanong · 3h ago
This post reminds me of the beauty of open source. Well done build and a great project summary!
This week I pulled out our big Meade 10” SCT and our small Meade 4” Newtonian to show my 7yo son the moon and Saturn from my parents Bortle 8 backyard. It was wonderful seeing his awe and surprise, and the fact that my parents were there to see it too.
That 10” SCT is on an old fork mount which is motorized but has no GOTO capabilities at all. I’ve also gone down the rabbit hole of researching mount options, thinking I could just buy my way out of it. However, as much as I like the idea of GOTO, a big part of the fun is finding the objects. So I’ve never been able to pull the trigger. I did buy a ZWO 585MC though, I’ve always wanted a dedicated cooled camera.
That said, we have lost way too many hours to trying to find objects. The Telrad isn’t always enough!
I’ve been looking into using my 3D printer and electronics know-how to build my way out of this. I was even thinking of swapping the motors for NEMA 17 steppers.
Then I stumbled upon PiFinder, and I think this project is going to be the exact balance of automation and Push-to guidance that I would like.
https://www.pifinder.io/
It’s a wonderful hobby and I think the latest in 3D printing and PCB manufacturing does mean we’re going to be able to solve a lot of these problems soon.
But most people don't learn the big CADs first, they learn Fusion. The few times I've tried Fusion, it's given me a headache. It's probably a bigger headache going the other direction.
Then, there are those who do all their CAD work in OpenSCAD. They scare me.
Meta comment: damn it's good to see something worthwhile at #1 on HN this morning.
That said, I recommend Autodesk Fusion free tier for anyone who just wants to get quality work done quickly. Some will refuse to use it on principle and that’s fine for them, but it really is quality software free for hobbyist use with trivial restrictions.
EDIT: Getting downvoted, presumably for suggesting a non-OSS software to get a job done. However I’d recommend anyone who just wants to get work done at least consider the options at their disposal. Not every software decision needs to be made on principle.
People sneer and tell me I’m going to get burned some day, but meanwhile I’ve been using it to great effect for many years for hobby projects that I can share around and edit easily.
Do you have a source for this? Or are you speculating?
> but it's out of principle
Great that it works for you. I have limited time for hobbies and I can’t justify making choices based on principle to avoid hypotheticals that even you admit aren’t going to happen.
> but don't complain other people should do the same because you can.
I’m not complaining. Anyone who wants to use a certain software based on principle is free to do so.
I’m sharing recommendations from my own experience and that of my peers. If the goal is to focus on the project you’re trying to do instead of fighting with software then people should be aware of their options.
It's amazing how much can be done, but anything that I think will take an hour, lasts 6. Many times into the night.
Free cad gets really complicated the moment you want to do surface modeling.
Sure. Skyfield is a python library to calculate that (among others). Right on the front page is an example how to calculate the azimuth and elevation of Mars: https://rhodesmill.org/skyfield/
I have experienced the pain of getting ekos/kstars/indi tools to work well on my personal scope. If you want to try driving indi devices via python I have some python code (it's not super polished, but it does enough for my needs): https://github.com/dahlend/contindi
some stuff may be somewhat glossed over, like usage of ground planes or which traces you're supposed to keep short, but when those are important they'll usually be mentioned, or even spelled out in a application note
The reason is that Trump is tariffing the hell out of the main Chinese telescope accessories manufacturer, ZWO. So if you can provide a non-Chinese alternative....
Think of trying to be Prusa 3D solution in the astrophotography area.
https://jlccnc.com/cnc-machining-quote
On the pcb front, I dread going through those final steps in the pcb ordering process. No matter how many parts I preorder, there is always something that is unavailable. So much churn in component availability.
I've got a Juwei-17 (Onstep harmonic drive with performance similar to the ZWO AM5N, but at nearly half the price) paired with the ZWO TC4 carbon fibre tripod.
The tripod has a load capacity of 50 kg (110 lbs) and weighs just 2.5 kg (5.5 lbs). The harmonic drive mount has a load capacity of 13 kg (29 lbs), or 18 kg (lbs) with a counterweight, and weighs 5.5 kg (12 lbs). Alltogether, the setup weighs about 8 kg (18 lbs) since I don't have to use counterweights.