Build your $399 harmonic mount with me, step by step

[Astro3dprintgeek]

🚀 New Video in the Series! 🚀

 

Hey everyone! I'm excited to share the second video in my DIY Harmonic Mount series. This one dives even deeper into the details for all the DIY astrophotography enthusiasts out there!

 

🔧 In this video, I cover:

✅ The Mount in Action – Watch it slew smoothly!

✅ OnStep Configuration – A detailed walkthrough of setting up OnStep for seamless operation.

✅ Mount Assembly – Step-by-step instructions to put everything together.

 

📸 While this video doesn’t feature real imaging under the stars just yet, it highlights the incredible motion and control that this $399 mount can achieve!

 

💡 If you missed the first video, don’t worry! This is part of an ongoing series where I explore building and using an open-source harmonic mount. All resources, files, and instructions are free for you to download and customize!

 

👉 Check out the full video here:

https://youtu.be/ViX7WukXNGQ

 

Let me know your thoughts in the comments—I’d love to hear your feedback! 🌌

[Astronomist]

Great project!

Do you plan on designing a wedge for it? A purpose designed wedge might be able to bring the centre of gravity closer to the tripod, which I suspect would significantly improve stability.

[LondonNeil]

Outstanding.   👏👏

[saac]

Great project and so well executed.  

Jim

[msacco]

Is this doable with a 3D printer? Or using CNC for the body enclosure is a must? How much difference would something like that make? And what material would be the best to print for this purpose?

[LondonNeil]

In the video he mentions printing the enclosure or that the cnc'd one he's had made is available from his sponsor for $100.  I'd pay the hundred I think,  although admittedly I know nothing about 3d printing,  but would worry a plastic one would flex.

 

 

[msacco]

38 minutes ago, LondonNeil said:

In the video he mentions printing the enclosure or that the cnc'd one he's had made is available from his sponsor for $100.  I'd pay the hundred I think,  although admittedly I know nothing about 3d printing,  but would worry a plastic one would flex.

 

 

I'm pretty sure he wrote that $100 is the price for a 3D print, and $220 for CNC which is quite expensive. If you consider all the materials, wedge needed, DEC clamp it gets closer to around $600-$700 I think.

[Astronomist]

14 hours ago, msacco said:

Is this doable with a 3D printer

I'd say probably not, 6061 aluminium is apparently about 5 times as stiff as the stiffest printed plastics.

[msacco]

28 minutes ago, Astronomist said:

I'd say probably not, 6061 aluminium is apparently about 5 times as stiff as the stiffest printed plastics.

Most common ones yeah, but stuff like PA-CF should be pretty comparable I think, at least in stiffness, but not sure about other properties.

Not sure which exact type would be best but stuff like that or similar might be a decent option, and while the filament is not super cheap it's not too expensive either.

[powerlord]

nice. I use PA-CF for most structural things. I mean, it wouldnt be like CNC ali, and you'd probably want to thicken it out a fair bit for a 3d print. Still, it will flex a little, but with the slow movements of mount, etc - I dunno - could be ok. Main thing I think would be to redesign it - a design for CNCed ali is gonna be rubbish as a 3d print - you need to design  for the material.

At the end of the day it's a nice project - but accuracy entirely dependant on the performance of the cheap aliexpress drives/gears.. time will tell if they are good enough or rubbish. Until he's actually got it guiding and measuring accuracy it could all be for nowt - not a critisism - it's just the way it is. No shortcuts really  - I do hope it works for him.

[msacco]

4 minutes ago, powerlord said:

nice. I use PA-CF for most structural things. I mean, it wouldnt be like CNC ali, and you'd probably want to thicken it out a fair bit for a 3d print. Still, it will flex a little, but with the slow movements of mount, etc - I dunno - could be ok. Main thing I think would be to redesign it - a design for CNCed ali is gonna be rubbish as a 3d print - you need to design  for the material.

At the end of the day it's a nice project - but accuracy entirely dependant on the performance of the cheap aliexpress drives/gears.. time will tell if they are good enough or rubbish. Until he's actually got it guiding and measuring accuracy it could all be for nowt - not a critisism - it's just the way it is. No shortcuts really  - I do hope it works for him.

Yeah agreed, though I did went ahead and purchased the gears already, aliexpress sale gave me $40 discount. Though I hope I'll manage to use it properly.

I want to purpose this for wide field rig so I think up to 300mm it might be decent enough with a 3D printed body, but without proper testing etc we can't really know

Edited November 28, 2024 by msacco

[powerlord]

yeh they are 66 quid each at the mo.

 

130 quid + 15 quid step board and 20 quid of steppers - price is now £170 to make yer own mount!!

[msacco]

12 minutes ago, powerlord said:

yeh they are 66 quid each at the mo.

 

130 quid + 15 quid step board and 20 quid of steppers - price is now £170 to make yer own mount!!

There's also a wedge to consider which a decent one costs around $100-$150.

A DEC clamp is around $30-$50 I think.

And then figuring whether a 3D print of any kind would be good enough or not, otherwise it's another $220.

I actually also thought of possibly adapting it to nema 17 planetary gearbox with 1:5 ratio. Planetary gearbox is known to have some backlash but when I tested my 1:27 one there was almost none, so could be a tradeoff between slightly more backlash and higher resolution. I think it even fits the current enclosure, or maybe needs just very minor adjustments.

[powerlord]

true.. I actually caught myself adding the things to my basket as a project before seeing sense - I have 2 az-gtis, S50..2 EQ6 prod, and EQ5.. last thing I need is another mount.

IF it can all be assembled quickly and IF it provides decent accuracy though, it could be a wee business for someone on the side - 5/600 quid mounts. probably a market. Saying that - there is a big difference between making on for yourself and/or a few mates and making a product to sell and support to the unwashed public - even if that 'public' are just us clowns.. I've been down that road once with a kickstarter 10 years ago with something, and it is a rabbit hole of time and effort.

[Astro3dprintgeek]

Hi, thanks for all the comments! 
The design is okay for both cnc and 3d print, this mount has a low payload capacity of 5/6kgs without cw, so  PLA-CF is absolutely okay for that weight. If you plan to add a cw and use the mount with heavier equipment the cnc version is better. 
The mount is cheap, the polar wedge is around 70usd on aliexpress, the clamp if you choose the svbony is 20 usd and you need only an adapter to use that. 

The cheap harmonic drives are absolutely okay, because both Ioptron/warp/zwo and so on, uses them, they for sure don't use the original harmonic drives (maybe only zwo)

[Astro3dprintgeek]

I'm modifying the enclosure so you could use a nema 17 with a planetary 1:5 and so, have a higher payload and accuracy

[msacco]

14 minutes ago, Astro3dprintgeek said:

I'm modifying the enclosure so you could use a nema 17 with a planetary 1:5 and so, have a higher payload and accuracy

Funny, I had this exact idea in mind and planned on doing this. I even checked with the harmonic drive seller on aliexpress because the gear uses 8mm shaft and not 5mm, we can purchase and replace the wave generator for $35 per axis, unless you had something else in mind?

Also, what do you think of backlash? I know planetary gears tend to have a lot of backlash but I tested some nema 17 planetary gear and I think it was pretty good with minimal backlash.

Edited November 30, 2024 by msacco

[msacco]

18 minutes ago, Astro3dprintgeek said:

Hi, thanks for all the comments! 
The design is okay for both cnc and 3d print, this mount has a low payload capacity of 5/6kgs without cw, so  PLA-CF is absolutely okay for that weight. If you plan to add a cw and use the mount with heavier equipment the cnc version is better. 
The mount is cheap, the polar wedge is around 70usd on aliexpress, the clamp if you choose the svbony is 20 usd and you need only an adapter to use that. 

The cheap harmonic drives are absolutely okay, because both Ioptron/warp/zwo and so on, uses them, they for sure don't use the original harmonic drives (maybe only zwo)

Would you mind sharing some links to those? And maybe a design for the adapter too if available?

Also regarding the 3d print material, I think PLA would be better than PLA-CF?

The only issue is heat resistance but I personally don't plan on leaving it outside.

PLA-CF makes it deal better with heat but also makes it more flexible, and not as strong as PLA, at least that's what I remember seeing?

Edited November 30, 2024 by msacco

[Astro3dprintgeek]

Hi, the links are in the video description and I don't have the adapter :(, pla-cf is a lot stiffer compared to pla

[LondonNeil]

I think it's super project and wonderful that the OP is sharing it. If a few others tinker and improve a few things,  iron out a few wrinkles,  then V2 or V3 will be fantastic.  I wonder if it needs a bigger capacity though? Obviously beefing bits up might make it much more costly,  but if a kit could be kept to say $650 and capacity doubled it could be really appealing.

As for ease of manufacture of a solid case, did you consider a simple 6 sided box, 6 rectangular pieces bolted together?  Perhaps drilling,  threading and counter sinking all the bolt holes or might be no cheaper but cncing the current case looks a lot of machining. 

[Astro3dprintgeek]

Hi, here you will news about the mount and how to increase the payload: https://astrophilos.com/news-for-version-v2-and-bom/

[powerlord]

jfi - there is now a full mount for less than £800 out there which has been reviewed. Your project is great and considerably cheaper, just mentioning it:

 

https://www.aliexpress.com/item/1005007884519284.html?spm=a2g0o.productlist.main.1.11c6gRj0gRj0u9&algo_pvid=6954cc62-7470-4233-a270-b7e9e80104f1&algo_exp_id=6954cc62-7470-4233-a270-b7e9e80104f1-0&pdp_npi=4%40dis!GBP!688.59!688.59!!!849.06!849.06!%40210385bb17334190469552930e974b!12000042705534232!sea!UK!100133513!X&curPageLogUid=cx2gfm48QBhG&utparam-url=scene%3Asearch|query_from%3A

there is a larger £800 one too - so both around, what 1/3rd the price of the ZWO versions

[skybadger]

And both onstep driven.