What does one do when frustrated at the lack of affordable, open source portable trackers? If you’re [OG-star-tech], you design your own and give it modular features that rival commercial offerings while you’re at it.
What’s a star tracker? It’s a method of determining position based on visible stars, but when it comes to astrophotography the term refers to a sort of hardware-assisted camera holder that helps one capture stable long-exposure images. This is done by moving the camera in such a way as to cancel out the effects of the Earth’s rotation. The result is long-exposure photographs without the stars smearing themselves across the image.
Interested? Learn more about the design by casting an eye over the bill of materials at the GitHub repository, browsing the 3D-printable parts, and maybe check out the assembly guide. If you like what you see, [OG-star-tech] says you should be able to build your own very affordably if you don’t mind 3D printing parts in ASA or ABS. Prefer to buy a kit or an assembled unit? [OG-star-tech] offers them for sale.
Frustration with commercial offerings (or lack thereof) is a powerful motive to design something or contribute to an existing project, and if it leads to more people enjoying taking photos of the night sky and all the wonderful things in it, so much the better.
Very cool project! I will have to build one of these.
I appreciate the work that went into the design and construction (and that awesome assembly video!), and I’m sure it works fine, but I think a few changes could make it better.
1) M3 screws driven into printed plastic is not good- the threads are so fine the holes will be easily stripped. Use screws made for plastic or even wood screws. Take apart any commercial plastic product held together by screws to see what proper screws for plastics look like.
2) don’t print this with PLA. There’s a good chance you’re going to transport it by car. If you leave this assembly in your car during the day, heat in the car will cause PLA parts to soften and distort, especially with belts under tension. Use PETG, or even better, ABS.
3) the accuracy of the motion will depend on the quality of the pulleys and shafts you use. If the center hole is oversized or drilled off center, or the shaft diameter is too small, the movement will not be uniform and will vary depending on the rotational positions of the pulleys. This means avoid cheapo parts sold for 3D printers. Buy quality pulleys made by industrial suppliers.
4) The whole thing looks as if it was designed to be made of metal, not plastic. Plastic parts are far more flexible than metal and should be designed “beefier” to prevent flexing. There are too many thin flanges (and no reason for them to be so thin) that screws pass through to hold everything together. In some of the photos with a camera mounted you can see parts visibly flexing. The main hinged assembly might have been better made using a metal door hinge with 3D printed parts attached, instead of the whole thing being printed.
5) Belt tension will cause the motor mount to flex. I’d use a motor with a longer shaft and add a bearing to the end of the shaft, or at least much thicker plastic to hold the motor.
In general, when you’re printing parts from flexible plastics, beefier is better. I start with solid blocks and remove only what is needed for function. That results in much sturdier parts that will work for a long time. I also use bosses to ensure alignment of parts where it matters. And FFS, don’t make anything you want to last, or will be transporting in a car, out of PLA.
I agree completely. I also suspect the design might work ‘well enough’ with these two minimal changes: Print in PC or PA-CF for strength and stiffness, and use threaded inserts.
Hi,
I am Ondřej Gejdoš, the creator of this project.
And i would like to clarify some things.
1. The design uses threaded inserts, they are included in the bom file. I know that screwing screws into 3d printed plastic would not be a good idea, from long term perspective.
2. With the choice of filament, I agree. But i recomend going a step further and using fiber reinforced filaments. If you want to save cost use fiber reinforced parts for the structural parts and regural abs for rest of the parts, to save cost. I recomend using for the fiber reinforced filaments a pet-cf filament or abs-gf or asa-cf. Pet-cf is the best choice for the tracker.
3. I think that there is a problem with that, that they used an old photo of a V1 and not a V2. The picture of the V2 is on the top of the article. Also i have tried to beef up some of the components, but soemtimes it’s not necesery. The gearbox, was made out of thiner parts, that when they are screwed together for a robust gearbox. Also choosing to print the files in right orientation will help a lot with strenght.
The hinge in V2 is good as metal one.
5. Belt tension will to cause the the motor mount to flex due to new design in V2 and instaled belt cover, that stops the part from moving fovard.
Cheers,
I hope you will enjoy building the V2.
Great project, thanks for your work!
Hi,
I am Ondřej Gejdoš, the creator of this project.
And i would like to clarify some things.
1. The design uses threaded inserts, they are included in the bom file. I know that screwing screws into 3d printed plastic would not be a good idea, from long term perspective.
2. With the choice of filament, I agree. But i recomend going a step further and using fiber reinforced filaments. If you want to save cost use fiber reinforced parts for the structural parts and regural abs for rest of the parts, to save cost. I recomend using for the fiber reinforced filaments a pet-cf filament or abs-gf or asa-cf. Pet-cf is the best choice for the tracker.
3. I think that there is a problem with that, that they used an old photo of a V1 and not a V2. The picture of the V2 is on the top of the article. Also i have tried to beef up some of the components, but soemtimes it’s not necesery. The gearbox, was made out of thiner parts, that when they are screwed together for a robust gearbox. Also choosing to print the files in right orientation will help a lot with strenght.
The hinge in V2 is good as metal one.
5. Belt tension will to cause the the motor mount to flex due to new design in V2 and instaled belt cover, that stops the part from moving fovard.
Cheers,
I hope you will enjoy building the V2.
Lots of points here. But there’s a dedicated GitHub and also inserts and a few things. They work well and quite a few people have made them
Sorry also a discord *
Go browse some of the builds and pics
You can also search the tracker on the astrobin site
Recently built and tried the v1 version. its really awesome going from few seconds to 30 seconds or more exposures on a nebula. 3d printed Plastic being 3d printed plastic , it has its limits. Then again going from nothing to 30 second subs on small ish (700 gram / 24oz) lenses is really awesome.
If I knew how to add a link to a picture I would have.
Rookie question: Why does it revolve around the centre of the lens stack, rather than the outmost lens where the light is initially collected? I remember something about 360° images being only flawless, when the outer lens is at the centre point. But given astro boffins are a smart bunch, I assume I am mistaken. I just want to understand it.
You are absolutely right, however stars and planets from a tiny lens / telescope perspective, everything is virtually at extreme infinity, that means the lens position itself doesn’t affect the image.
A 360 is also mildly different type of a capture but you could do a 360 astrophoto even if the camera is on a 100 meter pole.
Thank you Steven! I didn’t consider that with the scale of galaxies this becomes negligible.
hard to get a sense of how far things distanced from us. Here is an attempt:
https://joshworth.com/dev/pixelspace/pixelspace_solarsystem.html
I was disappointed by not seen “A moose once bit my sister”
Likely to balance the weight.
About 38 years ago I used one of those time switches that revovles once every 24 hours and can switch something on/off by putting those little pins in the right time position. I mounted this on hinged platform. Then I mounted my (analog) slr camera on top of the time switch and adjusted the angle of the hinged platform so it would be right for the latitude where I lived (the Netherlands). It worked beyond my expectations. I managed to capture beautifull pictures. It was a very crude build all together.