Space
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Coolness! Thank you. Thats a keeper!
The Farmers Daughter.0 -
Neil Armstrong's left extravehicular glove with sewn-on cuff checklist itemizing his duties as LMP Commander once on the surface of the moon.
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The latest USAF tactical satellite will be launched tonight. Wish I could be there to see it live. That has to be AMAZING.0
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To see it in better detail go here:
https://www.popchartlab.com/products/the-chart-of-cosmic-exploration
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Anyone else only see @thesunmoonandstars posts when she's quoted?
Also, I have a question about "seeing" the Milky Way galaxy. Since that's our galaxy, how does one see it? The way I understand it, it would be like seeing earth. Since we're on planet earth, it wouldn't look like a sphere from here, right?0 -
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PlaydohPants wrote: »Anyone else only see @thesunmoonandstars posts when she's quoted?
Also, I have a question about "seeing" the Milky Way galaxy. Since that's our galaxy, how does one see it? The way I understand it, it would be like seeing earth. Since we're on planet earth, it wouldn't look like a sphere from here, right?
It's like taking a picture of your house while you're inside it. You won't see the entire thing like the way you can see the Andromeda galaxy. It's like looking at an inside edge of the milkyway
An inside edge. Wow. Love this thread! Thank you for responding . Considering that earth is rotating, do we keep facing the same segment of the rest of the galaxy, or does it vary?0 -
Also, I have a question about "seeing" the Milky Way galaxy. Since that's our galaxy, how does one see it? The way I understand it, it would be like seeing earth. Since we're on planet earth, it wouldn't look like a sphere from here, right?
The galaxy is way less like a sphere than the Earth, it's closer to a dinner plate, but bulging in the middle. At least that's the current understanding. But it doesn't look like a circle from inside, it looks more like a thick line across the sky.
I've posted this before but it's probably useful right now. This is the Milky Way from Slate Peak in the North Cascades. The camera is more sensitive than the eye, so it's a little bit dimmer and it's less colorful too, when you're standing there.
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@PlaydohPants and @KeithMarcus
Let's go with a really basic analogy - but let's also stick with our space theme.
The sun is a star. It's not the biggest or the brightest start.
But it sure looks brighter than all the other stars.
Light comes from stars, and it goes in every direction, like this:
The closer you are to any light source, the more light will reach you. The further you are, the less light. Because tiny differences in angle get multiplied over distance. You can see how the beams spread out, they'll miss things that are far away.
You see light. Your eyes have lenses that gather it over a wide area and focus it onto a small area packed with light-sensitive cells.
A camera works the same way. But it's more sensitive - it "wastes" fewer incoming photons to inefficiency, so it requires fewer of them to recognize an image. The lenses people use for astrophotography are much larger (as a ratio of aperture width to optical length) than the eye, so they're able to gather more light.
People can do math, but we built calculators that can do it better. People can see, but we built cameras that can see better.3 -
I don't think I explained that very well at all. If you were able to make any sense of it, my hat's off to you.1
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astrophotography is a great hobby but gets expensive fast! my mount for my telescope cost me close to £1k and that was a cheap one!1
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Another thing, if anybody is interested in the physics of light and vision.
Here are some pictures of a 50 mm lens at different apertures:
You can plainly see that more light will pass through the lens at f/1.8 (first) than at f/22 (last). Smaller numbers mean a bigger opening, and more light gathering power - more brightness.
Your eyes work the same way. Your pupils dilate when it's dark, and when you're under the influence of certain drugs. They close down when it's bright out. That's why you can see well enough to walk under a full moon, or at noon at the beach. The lens in the pics above can open to f/1.8 and it can close to f/22, it can't get brighter or darker than that.
A 50 mm f/1.8 lens like this one costs about $100. A 50 mm f/1.4 lens is almost 2x brighter, weighs almost 2x as much, and costs $400. A 50 mm f/1.2 lens is brighter, heavier, and costs $1,500.
I don't know which one is most similar to human vision, but people can't go to the store and buy cat eyes. You sort of can do that with cameras. That's a huge part of why photos of the Milky Way look different than standing outside looking at it.1
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