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

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.

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 but if you need more accurate dimensions: 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.

For sufficiently dim targets, you absolutely need minutes long exposure. If you go for shorter bursts, you face two main challenges:

1) Not enough photons reach the sensor to distinguish the object you are trying to photograph from the noise floor of the sensor. This is by far the biggest reason to go for a tracking mount.

2) You bog your computer down in post processing. 50x1 minute images are far simpler to align than 500x6 seconds images.

Combine (1) and (2), and there's barely any reason to go for untracked shots. As for satellites, planes, clouds, or other kind of transient phenomena that can potentially ruin a shot, that's where you apply some kind of clipping over data (usually sigma clipping or some variation of it) and problem solved.

Interesting. I didn't realize there was a product/company with that name. Shoot-move-shoot is a common saying in motion controlled photography, and that was what I described.

I love the age we're in where anybody with a little know how can cheaply/affordably build something that was only available to the very well funded before. Each one of these are attempting the same thing, but trying to avoid the pain points each dev has seen from other products.

It can do both. They seem to use the product's name ("move-shoot-move") to refer to a mode which both tracks the stars and moves independently, creating a panning timelapse.

Haha, I noticed the same thing. I've started watching some of their tutorial videos, and have some other nit picking comments as well. However, these will probably get someone that's never done astrophotography up and running with the ability to get some great shots totally unachievable 15 years ago in this price range.

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).

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.