Yes, you can see normally - still call it daytime indeed - right out to Pluto and beyond. You can use this website by NASA to find out what time of day to go out of doors to experience light levels roughly equivalent to the surface of Pluto. Pluto Time - it's roughly the time of evening when the sky is just beginning to go pink if there's going to be a sunset.
This is what it is like where I live at "Pluto Time" just to give an idea of the light levels on Pluto.
You begin to lose colour vision at around 3 lux Mesopic vision
and direct sunlight at midday in tropics, is 130,000 Lux which I suppose is a reasonable estimate for full sunlight in a vacuum? At any rate it's going to be an underestimate rather than an overestimate.
So you would need to go out to sqrt(130,000/3) AU (distance from Earth to Sun) or about 208 AU.
That's way beyond the outside edge of the Kuiper belt. Even well into the Oort cloud you'd still be able to see in colour, easily
Oort Cloud
So - how far would you have to go for the brightness to be the same as a full moon?
Well at its brightest, seems the Moon can go up to 0.5 lux. Typically more like 0.3 lux.
So then we have sqrt(130,000/0.3) or about 660 AU, or about a hundredth of a light year.
Depending on whether you can read by moonlight, then you may still be able to read a book by the light of the sun out to this distance.
Can *you* read by moonlight? (Forum thread)
And you may also be able to discern colours. Some can.
I just tested myself, I can see red, blue and green clearly by moonlight, so I'd be able to see colours right out to a hundredth of a light year from Earth by the light of the sun. And I'd be able to read headlines and books in large text.
There is a lot of variation there between people. But most apparently can't see colours by moonlight (if you want to test yourself, then be sure to allow yourself a few minutes for dark adaptation).
On intensity of moonlight, this was the best I found: The Brightness of Moonlight
Goes into detail e.g. latitude dependence, and mentions many other things including the opposition effect, that it is somewhat brighter at around full moon due to reflection backwards from small glassy droplets that act like prisms in the lunar soil.
If anyone knows any other really good sources on the brightness of moonlight, do say!
Since you can see a bit even by starlight on a clear night, this might be worth calculating also. If you have reasonable night adaptation (been out in it for several hours for instance without torches or any other light pollution) and also have reasonably good night vision - which you would have if you lived there and spent a lot of time out of doors, then you can get around even in starlight.
Lux Light Level Chart
Anyway - so that's 0.001 lux, so our calculation then is
sqrt(130,000/0.001) AU
Or, 11,400 AU, or 0.18 light years.
Which also means - that 0.18 light years would be roughly the distance at which the sun would be equal in brightness to the rest of the night sky put together.
So actually that's the distance where the sky would be roughly double the brighness of a clear starry sky on Earth.
Almost anywhere even light years from Earth you'd be able to see a bit, just by the collective light from the stars and the milky way.
If you can get around on a clear starry night and avoid bumping into things, by starlight (when dark adapted after say an hour or two without a torch) - then you can also get around almost anywhere in our galaxy again without bumping into things except inside a dark gas cloud, or e.g. underground in a cave in an asteroid and such like places.
You'd need to be way out in space in between galaxies to have less ambient light than that, so long as you have a clear view of the stars.
This is what it is like where I live at "Pluto Time" just to give an idea of the light levels on Pluto.
This is what it would be like at midday on Pluto. Except of course that on Pluto if there is any liquid, it's either liquid nitrogen or liquid neon or some such. And not likely to be grass or houses though we won't be flying close enough to spot Pluto life on the remote possibility that there is life there, unless it has an obvious effect on the landscape. Even multicellular life, not quite the resolution to spot even likes of trees etc, though I think most would think they are unlikely, but there are ideas for exobiology using liquid nitrogen for instance, I think you'd be a brave exobiologist to say that multicellular life is absolutely impossible on Pluto, and even more so to say single cell life is impossible.
Many more images here: Pluto Time
HOW FAR OUT WOULD YOU NEED TO BE TO BEGIN TO LOSE COLOUR VISION
You begin to lose colour vision at around 3 lux Mesopic vision
and direct sunlight at midday in tropics, is 130,000 Lux which I suppose is a reasonable estimate for full sunlight in a vacuum? At any rate it's going to be an underestimate rather than an overestimate.
So you would need to go out to sqrt(130,000/3) AU (distance from Earth to Sun) or about 208 AU.
That's way beyond the outside edge of the Kuiper belt. Even well into the Oort cloud you'd still be able to see in colour, easily
HOW FAR OUT TO HAVE SAME BRIGHTNESS AS FULL MOON
So - how far would you have to go for the brightness to be the same as a full moon?
Well at its brightest, seems the Moon can go up to 0.5 lux. Typically more like 0.3 lux.
So then we have sqrt(130,000/0.3) or about 660 AU, or about a hundredth of a light year.
Depending on whether you can read by moonlight, then you may still be able to read a book by the light of the sun out to this distance.
Can *you* read by moonlight? (Forum thread)
And you may also be able to discern colours. Some can.
I just tested myself, I can see red, blue and green clearly by moonlight, so I'd be able to see colours right out to a hundredth of a light year from Earth by the light of the sun. And I'd be able to read headlines and books in large text.
There is a lot of variation there between people. But most apparently can't see colours by moonlight (if you want to test yourself, then be sure to allow yourself a few minutes for dark adaptation).
On intensity of moonlight, this was the best I found: The Brightness of Moonlight
Goes into detail e.g. latitude dependence, and mentions many other things including the opposition effect, that it is somewhat brighter at around full moon due to reflection backwards from small glassy droplets that act like prisms in the lunar soil.
If anyone knows any other really good sources on the brightness of moonlight, do say!
HOW FAR OUT FOR TYPICAL STARLIGHT
Since you can see a bit even by starlight on a clear night, this might be worth calculating also. If you have reasonable night adaptation (been out in it for several hours for instance without torches or any other light pollution) and also have reasonably good night vision - which you would have if you lived there and spent a lot of time out of doors, then you can get around even in starlight.
Lux Light Level Chart
Anyway - so that's 0.001 lux, so our calculation then is
sqrt(130,000/0.001) AU
Or, 11,400 AU, or 0.18 light years.
Which also means - that 0.18 light years would be roughly the distance at which the sun would be equal in brightness to the rest of the night sky put together.
So actually that's the distance where the sky would be roughly double the brighness of a clear starry sky on Earth.
Almost anywhere even light years from Earth you'd be able to see a bit, just by the collective light from the stars and the milky way.
If you can get around on a clear starry night and avoid bumping into things, by starlight (when dark adapted after say an hour or two without a torch) - then you can also get around almost anywhere in our galaxy again without bumping into things except inside a dark gas cloud, or e.g. underground in a cave in an asteroid and such like places.
You'd need to be way out in space in between galaxies to have less ambient light than that, so long as you have a clear view of the stars.
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
4.8m answer views110.3k this month
Top Writer2017, 2016, and 2015
Published WriterHuffPost, Slate, and 4 moreHuffPost, Slate, Forbes, Newsweek, Business Insider, and Science 2.0