[moi2388]

Can somebody ELI5 this to me?

The image with the 2 earths.. that only works if the camera is not also on the ground, but it is? How is the rotation of the object and the camera not identical? Why would it rotate ‘upwards’?

Also, if the issue is relative motion or rotation between camera and object, wouldn’t two sensors, one on the camera and one on the subject be able to solve this, since we can see if their rotations/movement match up or not?

[SamBam]

Imagine the camera were floating just above the surface of the Earth, and also that it had perfect image stabilization. This image stabilization would keep the camera always oriented in the same direction. Same direction relative to what? To the rest of the universe. So if it was pointing right at a star, it would continue pointing directly at that star as it went around and around the Earth. From our perspective on the surface, the camera would appear to be flipping over itself as it kept pointing at that star.

Unfortunately, this would be pretty bad for taking a picture of something that was right in front of the camera (relative to the surface of the Earth). You'd be in front of the camera, ready for your picture, and the camera would appear start rotating as it kept that distant star in view.

So with a perfect image stabilizer, this is what the camera is actually trying to do, even when standing on the Earth with a tripod. It actually senses the rotation of the Earth, and tries to cancel it out, just like it would cancel out your hands shaking. But while it's good to cancel out your hands shaking (because that's a motion that's independent of the subject of the photo), it's not good to cancel out the rotation of the Earth (because the subject of the photo is actually moving with you).

[thrdbndndn]

> Same direction relative to what? To the rest of the universe

By this logic, the Earth's revolution would also cause similar issue, and even worse. But in reality only the rotation does.

I think at least some part of your explanation does not calculate.

[Filligree]

The Earth's revolution around the sun? What makes you think it doesn't? It's just that the effect is 1/365 the size, on the same axis as the rotation.

[Karellen]

The same axis of rotation? Pretty sure they're about 23° off.

[Filligree]

Alright, close-ish to the same axis.

[SamBam]

It does. A perfect gyro will remain on a single axis relative to the rest of the universe while the Earth goes around the sun, and while the galaxies swirl around.

I'll leave it to you to figure out how "perfect" it would need to be, and what the actual error that the stabilizer would need to account for if the gyroscope is accurate enough to detect the motion of the Earth around the sun, compared with the error created by the Earth's rotation.

[moi2388]

That makes sense. It doesn’t make sense why you wouldn’t simply correct for that, or why having 2 sensors wouldn’t fix it?

[llm_trw]

The position of the gyro is attached to the earth surface but its orientation is not. See Foucault's Pendulum.

[moi2388]

Thanks! That makes it incredibly obvious

[mikewarot]

We all want to keep missiles out of the hands of bad people.

Parts to make really good cameras could be taken out and used in missiles, to tell them where to go.

So we now have laws to keep those really good parts out of cameras, for safety. Cameras still work fine, but you need a tripod to get good pictures when it's dark out.

[exitb]

https://youtu.be/1zJ9FnQXmJI