Why aren't the stars more visible in the background? Does it have to do with the camera's exposure?
From a million miles away, NASA camera shows moon crossing face of Earth
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Re: From a million miles away, NASA camera shows moon crossing face of Earth
#12Why aren't the stars more visible in the background? Does it have to do with the camera's exposure?
Earth is a sunlit object in this picture, the luminosity is the same level as during the day on earth - would you see stars in your photos if you took a correctly exposed photo of something during daylight on earth? I don't think this would happen :) The dynamic range difference between day light objects on earth and the stars on the sky is huge.
Re: From a million miles away, NASA camera shows moon crossing face of Earth
#13Is this the real reflectance of the moon? Seems so dark. Usually we see the moon at night surrounded by night sky, which probably skews our perception of the real color of the surface material.
Probably because that's the Dark Side of the Moon?
Re: From a million miles away, NASA camera shows moon crossing face of Earth
#14Maybe as interesting is where this satellite is: The Lagrange L1 point. The 5 Lagrange points in essence allow orbiting bodies to break Kepler's laws. A satellite a million miles closer to the Sun shouldn't have the same orbital period as the Earth... but it does.
That's because Kepler only assumes 1-body interaction! With 2-body, or N-body, then you get lagrange points. It doesn't "break" Kepler's law, it is just that Kepler law doesn't apply in 3-body interactions.
Re: From a million miles away, NASA camera shows moon crossing face of Earth
#15Why aren't the stars more visible in the background? Does it have to do with the camera's exposure?
Note that the Moon is fully lit by the Sun (it's a "full Moon" from the perspective of the satellite). And it's gray on the picture, as the Earth is significantly brighter.
Now, you can check it yourself, take the best camera you can have, go one night when the Moon is full somewhere outside of the city where you see the stars and then try to make a photo where on the photo both the stars and the Moon surface are visible at the same time. It simply can't work, the light of the stars is very faint, as soon as you see any details of the surface on the photo you take the stars will surely be invisible. Our eyes are still much better than any camera we can produce.
Re: From a million miles away, NASA camera shows moon crossing face of Earth
#16Why aren't the stars more visible in the background? Does it have to do with the camera's exposure?
Earth is a sunlit object in this picture, the luminosity is the same level as during the day on earth - would you see stars in your photos if you took a correctly exposed photo of something during daylight on earth? I don't think this would happen :) The dynamic range difference between day light objects on earth and the stars on the sky is huge.
The satellite is 1 million miles away from Earth at the L1 Lagrange point. What is it about optics that allows us to compare a photo of the stars taken at such a distance with one taken from the surface of the earth? [Edit: "compare", in the sense of understanding whether or not the stars will or won't show up in each case. I get that the laws of optics are the same throughout the universe.]
> The dynamic range difference between day light objects on earth and the stars on the sky is huge.
I agree, but would a person sitting in the satellite see stars if they looked in that direction? If so, do our eyes just have better dynamic range than the camera used by the satellite?
Re: From a million miles away, NASA camera shows moon crossing face of Earth
#17Should I be able to see Earth orbiting satellites in this picture?
Re: From a million miles away, NASA camera shows moon crossing face of Earth
#18Should I be able to see Earth orbiting satellites in this picture?
How close are satellites to the spacecraft that took these photos? Well, it's about a million miles from Earth, generally the farthest satellites away from Earth are at about 40,000km altitude in geostationary orbit, which would put them maybe 4% closer to the spacecraft than Earth, so it wouldn't affect perspective hardly at all.
So that leaves resolution and physical size.
How big are satellites? About the size of cars or maybe a bus?
Can you see cars in this picture?
Re: From a million miles away, NASA camera shows moon crossing face of Earth
#19Should I be able to see Earth orbiting satellites in this picture?
No more than you'd expect to be able to see a car, I don't think.
Re: From a million miles away, NASA camera shows moon crossing face of Earth
#20Should I be able to see Earth orbiting satellites in this picture?
You mean like the moon? Yes.
You mean like meteosat? No. A 4 metre wide object is going to be such a small proportion of the size of a single pixel that it will be completely invisible.