12 ms·

OpenAstroTracker: A cheap 3D-printed tracking mount for DSLR astrophotography

126 points by reimertz 5y ago

deleted 5y ago
[deleted]
MetaWhirledPeas 5y ago
This is nice! Is there something similar that's simpler and dumber, that just handles the rotation but doesn't try to locate objects?
- teraflop 5y ago
  Here's a very simple one-axis tracker using a 24-hour clock movement and a 3D-printed GoPro mount: https://hackaday.com/2018/06/03/3d-printed-clockwork-star-tracker/ https://hackaday.com/2018/06/03/3d-printed-clockwork-star-tr...
  - rripken 5y ago
    That really is a great hack if your camera is light enough. Genius.
- rripken 5y ago
  Barn door trackers. https://en.wikipedia.org/wiki/Barn_door_tracker https://en.wikipedia.org/wiki/Barn_door_tracker https://hackaday.com/2013/08/08/building-a-barn-door-tracker-for-astronomical-photography/ https://hackaday.com/2013/08/08/building-a-barn-door-tracker...
foobarbecue 5y ago
I use a Soloshot to film my surfing. I'm annoyed with the buggy closed source software and wondering if I could replace it with one of these...
dylan604 5y ago
Dupe: https://news.ycombinator.com/item?id=26930958 https://news.ycombinator.com/item?id=26930958
- app4soft 5y ago
  > Dupe Yep, only 17 days ago. And I already posted link to its GitHub repo.[0] [0] https://news.ycombinator.com/item?id=26931253 https://news.ycombinator.com/item?id=26931253
dukeofdoom 5y ago
How does this compare to something like move-shoot-move? I think that one costs only $200. Is it even worth it to DIY.
- dylan604 5y ago
  Shoot-move-shoot does what it sounds like. It moves the platform, allows time for the movement to settle, snaps the shot, then moves again. Astrotrackers like this are constantly moving at the same rate that the earth spins on its axis. This allows for the subject to remain in the same poistion in the frame during super long exposures. Depending on the accuracy of the polar alignment and the focal length of the lens, tracking allows for shots to go from <20 seconds to multiple minutes long for one exposure.
  - andrewxdiamond 5y ago
    What is the benefit of using robotics to move the camera over image stabilization software in post? Is it simply image quality? Or are there more trade offs?
    - dukeofdoom 5y ago
      You need a long exposure to let in enough light for stars to become clearly visible. If you expose for longer than ~ 30 seconds, then the earth will rotate enough to start causing star trails. This will physically rotate the camera to counteract earths rotation.
    - dylan604 5y ago
      The is a common question, but there are certain things that are just better done in camera than post. Then there are situations where a combination of in camera + post provides optimum results. Astrophotography is one that can and does use both. The longer you can expose, the more information obtained. For ultimate long shots, you need to compensate for the earth's rotation. You continue to snap away all night, and then take those images into post where you stack the images. The stacking software adds the data together resulting in a single image that is the equivalent of a single image with an exposure time equaling the sum of each shot. Why do this? If you do single long exposure, there is a very good chance your image will have an airplane fly through, a satellite streak by, or something more terrestrial like a fellow stargazer shining a laser through your frame, car headlights, etc. Taking a series of short exposures limits those issues, and if it happens, you throw out that shot and only loose 45-60 seconds instead of 15 minutes. Stacking can also use shots you take when the lens is covered called dark frames. You take this for the same exposure time as the normal shots. This provides a noise pattern that builds up in any electronic sensor as the heat builds up from staying energized for so long (as well as natural summertime heat). That noise pattern can then be subtracted by the stacking software. The stacking software can also realign the images so you can use shots from multiple shoot days (er, nights).
emptybits 5y ago
This is quite brilliant. Here's another approach to tracking, employed by Pentax and maybe others: Use 5-axis sensor movement to track stars (i.e. use the motors which move the sensor for in-body stabilization) Given GPS coords, software can do this to the limits of sensor movement afforded by the camera body. I don't have a Pentax but modern models can apparently track for at least 4 minutes.[1] (!) In theory, official or unofficial firmware for other models of camera might be able to do the same. [1] https://milkywayphotographers.com/article/2021/01/21/pentax-astrotracer-guide-what-it-is-and-how-to-use-it/ https://milkywayphotographers.com/article/2021/01/21/pentax-...
- wtallis 5y ago
  I think this requires not just a GPS fix but also fairly accurate heading information from an electronic compass and tilt information from the camera's accelerometer, because shifting the sensor in the right direction requires knowing which part of the sky the camera is pointed at. (I haven't bought the astrotracer add-on for my Pentax because it's crazy expensive for what it is, but it should be at least a bit more than just a GPS receiver.)
  - martyvis 5y ago
    Surely in camera, it is just a matter of taking a shot, wait an interval, take another shot, then shift/rotate the two images until X number of bright spots line up and then form a new composite, rinse and repeat. If you have a motor in the camera for stabilising you can use that shift/rotate parameter to move the sensor for the next shot.
    - TaylorAlexander 5y ago
      Modern cameras can physically move the sensor inside the camera. It is called IBIS or In Body Image Stabilization. Taking one long exposure I imagine would better pick up on faint sources of light compared to multiple short exposures.
      - 5y ago
avmich 5y ago
Tried to find some mechanical data on this and couldn't :( . What's the size of it, what's the working speed of motors?..
- deleted 5y ago
  [deleted]
- dekhn 5y ago
  literally everything is on the website.
  - avmich 5y ago
    If that information is there, it's definitely not easy to find. Can you share a link?
    - dekhn 5y ago
      Your questions are: how big is it and what are the working speeds of the motors. It is this big: https://wiki.openastrotech.com/alu-oat.jpg https://wiki.openastrotech.com/alu-oat.jpg but if you need more accurate dimensions: https://wiki.openastrotech.com/en/OpenAstroTracker/Printing https://wiki.openastrotech.com/en/OpenAstroTracker/Printing (select the appropriate parts aand look at their dimensions in a 3D STL viewer. Those are in millimeters) and then look at the youtube video where you can see it in context. The motors: the working speed of the motor is identical to the speeds required to keep the scope aligned. For one of the axes, that means it causes the system to do a full 360 rotatation every 24h. Steppers (both the small kind and the big kind) can work at 1500RPM but this is irrelevant- we care much more about precise small movements.
      - avmich 5y ago
        Thank you very much; I was hoping for some more direct answers, e.g. diameter of the ring is 400 mm and speed of rotation is up to 15 RPM. I'd like to do something significantly different with this design (outside of astro-photography, so different properties and ranges are relevant) and was interested in existing capabilities. I saw the video and knew approximate values, I just wanted to see explicit specs - like blueprints for parts with sizes, or capabilities of motor-belt-ring coupling.
jmpman 5y ago
Let’s say that I know precisely where the AstroTracker is - X,Y,Z all within ~ 1 centimeter, and my goal is to point a laser in a specific vector from the base, how accurately could I do that?
jnsie 5y ago
Man, wish there was something like this for the AWB (Astronomers Without Borders) Opensky telescope!

126 points by reimertz 5y ago

deleted 5y ago

[deleted]

This is nice! Is there something similar that's simpler and dumber, that just handles the rotation but doesn't try to locate objects?

teraflop 5y ago
Here's a very simple one-axis tracker using a 24-hour clock movement and a 3D-printed GoPro mount: https://hackaday.com/2018/06/03/3d-printed-clockwork-star-tracker/ https://hackaday.com/2018/06/03/3d-printed-clockwork-star-tr...
- rripken 5y ago
  That really is a great hack if your camera is light enough. Genius.
rripken 5y ago
Barn door trackers. https://en.wikipedia.org/wiki/Barn_door_tracker https://en.wikipedia.org/wiki/Barn_door_tracker https://hackaday.com/2013/08/08/building-a-barn-door-tracker-for-astronomical-photography/ https://hackaday.com/2013/08/08/building-a-barn-door-tracker...

foobarbecue 5y ago

I use a Soloshot to film my surfing. I'm annoyed with the buggy closed source software and wondering if I could replace it with one of these...

dylan604 5y ago

Dupe: https://news.ycombinator.com/item?id=26930958 https://news.ycombinator.com/item?id=26930958

app4soft 5y ago
> Dupe Yep, only 17 days ago. And I already posted link to its GitHub repo.[0] [0] https://news.ycombinator.com/item?id=26931253 https://news.ycombinator.com/item?id=26931253

dukeofdoom 5y ago

How does this compare to something like move-shoot-move? I think that one costs only $200. Is it even worth it to DIY.

dylan604 5y ago
Shoot-move-shoot does what it sounds like. It moves the platform, allows time for the movement to settle, snaps the shot, then moves again. Astrotrackers like this are constantly moving at the same rate that the earth spins on its axis. This allows for the subject to remain in the same poistion in the frame during super long exposures. Depending on the accuracy of the polar alignment and the focal length of the lens, tracking allows for shots to go from <20 seconds to multiple minutes long for one exposure.
- andrewxdiamond 5y ago
  What is the benefit of using robotics to move the camera over image stabilization software in post? Is it simply image quality? Or are there more trade offs?
  - dukeofdoom 5y ago
    You need a long exposure to let in enough light for stars to become clearly visible. If you expose for longer than ~ 30 seconds, then the earth will rotate enough to start causing star trails. This will physically rotate the camera to counteract earths rotation.
  - dylan604 5y ago
    The is a common question, but there are certain things that are just better done in camera than post. Then there are situations where a combination of in camera + post provides optimum results. Astrophotography is one that can and does use both. The longer you can expose, the more information obtained. For ultimate long shots, you need to compensate for the earth's rotation. You continue to snap away all night, and then take those images into post where you stack the images. The stacking software adds the data together resulting in a single image that is the equivalent of a single image with an exposure time equaling the sum of each shot. Why do this? If you do single long exposure, there is a very good chance your image will have an airplane fly through, a satellite streak by, or something more terrestrial like a fellow stargazer shining a laser through your frame, car headlights, etc. Taking a series of short exposures limits those issues, and if it happens, you throw out that shot and only loose 45-60 seconds instead of 15 minutes. Stacking can also use shots you take when the lens is covered called dark frames. You take this for the same exposure time as the normal shots. This provides a noise pattern that builds up in any electronic sensor as the heat builds up from staying energized for so long (as well as natural summertime heat). That noise pattern can then be subtracted by the stacking software. The stacking software can also realign the images so you can use shots from multiple shoot days (er, nights).

emptybits 5y ago

This is quite brilliant. Here's another approach to tracking, employed by Pentax and maybe others: Use 5-axis sensor movement to track stars (i.e. use the motors which move the sensor for in-body stabilization) Given GPS coords, software can do this to the limits of sensor movement afforded by the camera body. I don't have a Pentax but modern models can apparently track for at least 4 minutes.[1] (!) In theory, official or unofficial firmware for other models of camera might be able to do the same. [1] https://milkywayphotographers.com/article/2021/01/21/pentax-astrotracer-guide-what-it-is-and-how-to-use-it/ https://milkywayphotographers.com/article/2021/01/21/pentax-...

wtallis 5y ago
I think this requires not just a GPS fix but also fairly accurate heading information from an electronic compass and tilt information from the camera's accelerometer, because shifting the sensor in the right direction requires knowing which part of the sky the camera is pointed at. (I haven't bought the astrotracer add-on for my Pentax because it's crazy expensive for what it is, but it should be at least a bit more than just a GPS receiver.)
- martyvis 5y ago
  Surely in camera, it is just a matter of taking a shot, wait an interval, take another shot, then shift/rotate the two images until X number of bright spots line up and then form a new composite, rinse and repeat. If you have a motor in the camera for stabilising you can use that shift/rotate parameter to move the sensor for the next shot.
  - TaylorAlexander 5y ago
    Modern cameras can physically move the sensor inside the camera. It is called IBIS or In Body Image Stabilization. Taking one long exposure I imagine would better pick up on faint sources of light compared to multiple short exposures.
    - 5y ago

avmich 5y ago

Tried to find some mechanical data on this and couldn't :( . What's the size of it, what's the working speed of motors?..

deleted 5y ago
[deleted]
dekhn 5y ago
literally everything is on the website.
- avmich 5y ago
  If that information is there, it's definitely not easy to find. Can you share a link?
  - dekhn 5y ago
    Your questions are: how big is it and what are the working speeds of the motors. It is this big: https://wiki.openastrotech.com/alu-oat.jpg https://wiki.openastrotech.com/alu-oat.jpg but if you need more accurate dimensions: https://wiki.openastrotech.com/en/OpenAstroTracker/Printing https://wiki.openastrotech.com/en/OpenAstroTracker/Printing (select the appropriate parts aand look at their dimensions in a 3D STL viewer. Those are in millimeters) and then look at the youtube video where you can see it in context. The motors: the working speed of the motor is identical to the speeds required to keep the scope aligned. For one of the axes, that means it causes the system to do a full 360 rotatation every 24h. Steppers (both the small kind and the big kind) can work at 1500RPM but this is irrelevant- we care much more about precise small movements.
    - avmich 5y ago
      Thank you very much; I was hoping for some more direct answers, e.g. diameter of the ring is 400 mm and speed of rotation is up to 15 RPM. I'd like to do something significantly different with this design (outside of astro-photography, so different properties and ranges are relevant) and was interested in existing capabilities. I saw the video and knew approximate values, I just wanted to see explicit specs - like blueprints for parts with sizes, or capabilities of motor-belt-ring coupling.

jmpman 5y ago

Let’s say that I know precisely where the AstroTracker is - X,Y,Z all within ~ 1 centimeter, and my goal is to point a laser in a specific vector from the base, how accurately could I do that?

jnsie 5y ago

Man, wish there was something like this for the AWB (Astronomers Without Borders) Opensky telescope!