How do people take photos of galaxies with 50 hours of exposure? How is it possible to aim at the same spot while earth is doing more that 2 rotations in that time?
In: Technology
Keep in mind that the movement of the Earth is very very slow. 15° an hour is as fast as it turns. So you can make a very large object move very steadily in the direction opposite the movement of the Earth it basically stays pointing at exactly the same part in the sky.
The farther away something is the fewer of its photons you receive an hour or a minute or a second. So they’ll very large telescopes collect individual photons over a long period of time.
when you photograph something here on Earth like your cat you are also collecting individual photons but there are so many of them that you get them all at once.
For ground-based telescopes there’s a lot of extra work to do because it’s not just motion but clouds and the waivering of the air due to thermal changes and stuff like that.
so all photography and indeed all sensing of light and radiation is based on the cumulative effect of individual photon events.
Making images of Small distant objects, or large distant objects that appear small to us because they’re so far away, involved collecting enough photons to make a picture. The delays and the complicated math and advanced photography and just plain keeping things aimed is an ongoing process of improvement.
We’re literally talking clock motors moving entire well-balanced telescopes. Like wound up clock motors powered by springs back in the day.
telescopes are extremely well balanced and extremely precision manufactured and many of the pictures we take today we’re not possible before the advent of computers because the finest grain corrections couldn’t be done mechanically.
One of the side things in this whole issue is like how we no longer have to use as many x-rays to x-ray your body. With precision electronic receptors instead of film it takes way fewer x-ray photons to map and display the structures of the body.
Same thing for space.
And for all that I make it sounds super subtle, it’s all just basic trigonometry. You can use the light from several galaxies that are many many light years away and aren’t the galaxy you’re looking at, to make sure that you’re aimed at the galaxy you are looking at simply because those multiple photons coming in from those multiple angles formed triangles compared to the thing you actually care about.
The thing about math and science is it’s the same basic techniques used again and again to create more complex and more subtle techniques essentially by comparing and contrasting what you have and what you want to know.
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