What does the sky look like to human eyes from orbit?

Question

There are numerous pictures, obviously, of the blackness of space from the shuttle, the space station, and even the moon. But they all suffer from being from the perspective of a camera, which is not sensitive enough to pick up the stars in the background when compared to the bright foreground objects (the limb of the Earth, the station, moon, etc). I've seen some photos that show a few of the brightest stars, but nothing special.

Are there any photos or eye witness accounts from astronauts of what it looks like to a human with night-adjusted vision? If I were in an orbit similar to the space station and looked away from the Earth, would I be able to see more stars than I ever could on Earth, or would it only be marginally better than the best terrestrial night viewing?

Answer 1

I haven't been to space :( and don't know of any accounts to point you to but I suspect that the view would be marginally better than that on earth.

First, the "black of space" would be really black i.e. no light. Even in dark skies there is a bit of scattered light in the atmosphere (even if just from scattered starlight) so you'd have higher contrast.

Additionally, you wouldn't have any "seeing" effects, the bluring of the starlight by the shifting atmosphere so the stellar images would be more concentrated. Not that you'd probably be able to consciously notice. The net effect would be to sharpen the stellar image on you eyes and increase the contrast a bit more.

I suspsect you'd see a few more stars for the above reasons, especially the latter as you eyes would have a better chance to detect light from the sharper stellar images. However, it wouldn't be a huge amount more as the stars are intrinsically faint and your eyes are only so senstive.

Answer 2

It will be better than observing from Earth, especially if you observe while in the shadow of the Earth. This is because the atmosphere absorbs some of the light entering the atmosphere, making it harder to see dimmer or further away stars. Like how in fog it is easier to see a objects closer to your than further away.

The atmosphere also scatters light. This affects blue light (shorter wavelength) more than red light, so this will slightly alter the appearance of stars, making them seem slightly red than the actually are (because more blue light is being scattered and is therefore not reaching your eye).

The Earth's atmosphere is also not uniform in density, pockets of different densities move around, as they do so they refract the light randomly. Cold air is more dense than hot air, and the greater the density of the air, the more the light is refracted. This provides the twinkling effectwe see from Earth, and can make stars appear as though they are changing colour slightly.

Additionally some light coming from Earth will reflect off the atmosphere and backdown, drowning out stars, this is the orange glow above cities. It also depends on whats in the air the more dust and particles in the air the more the [negative] effect the atmosphere will have on viewing conditions.

Stars near the horizon on Earth will be even more effected as the light coming from them will have travelled through more atmosphere to get to your eye, than stars directly overhead. This doesn't happen in space either.

This is why telescopes are better placed on mountains (eg Mauna Kea in Hawaii, is the tallest mountian on earth, although not the highest, but there is very little light pollution and the weather is stable) and will get even better quality in space (eg Hubble Space Telescope), because there is no atmosphere to get in the way. So yes the stars will be brighter in orbit and will be clearer without twinkling.

See this question on the NASA site as well