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Jupiter picture processed by one of citizen scientists

Picture above is artificially proceeded by one of the citizen scientists working for NASA. It was composed from monochromatic pictures taken by space probe Juno, flying in Jupiter system. Usually ships like Juno has only monochromatic, but sensitive cameras, and take such pictures using filters with basic colours. I'm not an expert but I suppose it is some trade off between accuracy and sensitivity. A lot of people are working on such pictures, and results are marvelous, just as you may see above!

The Sun seen from this distance is just bright, but nothing than a star. It is not a circle on the sky anymore. It is rather a bright point in the space.

Photos taken on the Earth's Moon looks like very contrast, and in fact, even if bright parts of the pictures are very clear, because of lack of the atmosphere, shadows are very deep. Probably staying on Moon ground you cannot look a lot in shadows on the Moon because there's no atmospheric scattering of the sunlight. So astronauts probably has its own light sources - just lamps - in order to operate in shadowed areas ( I am not sure it it actually was like that).

Human eye can see colors if there is enough light, and proper color vision require "natural sunlight", if ambient light is different than that, our perception of colors is different. What is more when at dawn or dusk, and at night, humans brain switches off color vision, and use monochromatic view instead.

So here it is a question: if a person, an Jupiternaut, would be orbiting Jupiter as Juno does, would she see anything with naked eye? Is there enough light to use color vision, or it remains a night situation in earth rather?

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  • $\begingroup$ Why downvote? :) $\endgroup$ – kakaz Jan 20 '18 at 17:32
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    $\begingroup$ Not my downvote, but you should have considered this fact also: Earth-based observers, looking through telescopes in real time, see the coloration of Jupiter due to reflected sunlight. An observer closer to Jupiter would receive a greater intensity. $\endgroup$ – Bill N Jan 20 '18 at 17:45
  • $\begingroup$ Yes, of course. But in that case, colors are not so bright as on the pictures processed. It passed through earth's atmosphere, however, so in space should be brighter. $\endgroup$ – kakaz Jan 20 '18 at 17:48
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    $\begingroup$ Combining several monochromatic images to create a so-called false color image is a common technique in astronomy. It can make details pop out that would be harder to see in the individual monochrome images. They call them "false color" to remind you that the images do not show the colors that you would see if you could view the object with your naked eye. $\endgroup$ – Solomon Slow Jan 20 '18 at 18:18
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    $\begingroup$ If you know the properties of the filters, you can recreate a pretty much accurate result. The use of a monochrome camera is probably because it has the optimal resolution while a bayer matrix in a color camera doesn't. Personally I'd think the colors you see in a large newton reflector high up in the mountains are roughly accurate. $\endgroup$ – Haunt_House Feb 20 '18 at 11:38
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Jupiter is five times as far away as the Earth is from the Sun. The reduction in sunlight is roughly a factor of 25.

A sunlit blue sky has a luminance of around $10^4$ cd/m$^2$, but photopic (colour) vision, works at levels a thousand times lower than this. At a reduction of only 25 times (and even allowing for an albedo of 30%) there should be plenty of light for colour vision to work.

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  • $\begingroup$ It is probably just my misunderstanding, but photopic vision require about 10^(-3) cd ( candelas) and more, Wikipedia says. But you are using lux as a unit of measure, so it is related to some kind of surface. Could you explain it? $\endgroup$ – kakaz Jan 20 '18 at 17:45
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    $\begingroup$ @kakaz 10 cd/m^2 (according to wikipedia). It has to be based on a flux. $\endgroup$ – Rob Jeffries Jan 20 '18 at 17:48
  • $\begingroup$ From Wikipedia: "The human eye uses scotopic vision under low-light conditions (luminance level 10−6 to 10−3.5 cd/m2), and mesopic vision in intermediate conditions (luminance level 10−3 to 100.5 cd/m2).". But I was asking why do you use lux, instead of candelas? How can I recalculate one to another, in order to check if you are not cheating? $\endgroup$ – kakaz Jan 20 '18 at 17:51
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    $\begingroup$ @kakaz I have linked to wikipedia and it says 10 cd/m$^2$. Not 10 cd. If you look I have removed the reference to lux, which differs from luminance by the solid angle subtended. Given that the eye can look at of order a few steradians, the difference is not important. $\endgroup$ – Rob Jeffries Jan 20 '18 at 17:54
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    $\begingroup$ I've seen Jupiter through small reflectors in color (3", 4.5"), so using a 20 inch newtown should be a big surplus of light. Getting a used telescope is fun. Making one yourself is fun, too. $\endgroup$ – Haunt_House Feb 20 '18 at 11:43

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