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I just saw a documentary about New Horizons and Pluto with plenty of photos New Horizon had taken of Pluto. All these photos were very bright, like Earth would be during the day. Considering the distance between Pluto and the sun I suspect the brightness of the photos has been manipulated.

So, if you would be standing on Pluto's equator when the sun is in zenit, how bright would it be?

Pluto

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    $\begingroup$ "I suspect the brightness of the photos has been manipulated." Can you imagine how crappy virtually all astronomical images would look if they were adjusted to present the same intensity that an actual human would perceive if floating in outer space and looking at them? One half would be invisible and the other half would blind, burn or even cook or vaporize the viewer! $\endgroup$
    – uhoh
    Nov 1, 2020 at 0:59
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    $\begingroup$ Not "manipulated", but presumably taken with detectors which - like the sensor in your digital camera - are more sensitive than the human eye. $\endgroup$
    – jamesqf
    Nov 1, 2020 at 1:47

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Back when New Horizons was preparing for its flyby back int 2015, NASA's website set up a tool to allow you to experience the brightness of light at High Noon on the subsolar point on Pluto.

From Space.com: NASA's 'Pluto Time' Shows You How Bright It Is on Dwarf Planet

To an observer on Pluto's surface, the sun would be about 1,000 times dimmer than it is here on Earth, NASA officials said. At noon, the sunlight would be strong enough for you to read a book, they added. (Though it might be hard to keep your eyes from straying upward to take in the exotic Pluto sky, with the big moon Charon looming just overhead.)

The NASA Pluto Time website can be found here:

https://solarsystem.nasa.gov/planets/dwarf-planets/pluto/plutotime/

In general, the time it will return for you will be a little bit after sunset (or before sunrise), but still bright enough for pretty good vision. For my current location, at about 41° N latitude , on October 31, 2020, it's giving me a local time of five minutes after sunset.

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These two calcs agree pretty well:

The Sun's magnitude from from Pluto is -18.7

m = -18.75 magnitudes

That's quite a bit brighter than a full moon, so you'd be able to read by it.

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  • $\begingroup$ Would it be bright enough for color vision, or just black-and-white? $\endgroup$
    – nick012000
    Nov 1, 2020 at 6:01
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    $\begingroup$ @nick012000 if my math is right, -18.7 mag corresponds to about 75 lux illumination at noon. Full color vision requires at least 10 lux, with partial color perception down to around 0.01 lux. So, should be fine. $\endgroup$
    – hobbs
    Nov 1, 2020 at 8:06
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From Pluto, the Sun is point-like to human eyes, but still very bright, giving roughly 150 to 450 times the light of the full Moon from Earth (the variability being due to the fact that Pluto's orbit is highly elliptical, stretching from just 4.4 billion km to over 7.3 billion km from the Sun).

https://www.discovermagazine.com/the-sciences/bafact-math-how-bright-is-the-sun-from-pluto

Nonetheless, human observers would find a large decrease in available light: the solar illuminance at Pluto’s average distance is about 85 lx, which is equivalent to an office building hallway’s illuminance or a toilet’s lighting.

https://en.wikipedia.org/wiki/Extraterrestrial_sky#Pluto_and_Charon

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    $\begingroup$ Might be worth pointing out how wide-ranging is the human perception of brightness: From 100 Klux in bright sunlight to ~1 lux for full Moon. That's five orders of magnitude. 85 Lux is plenty of light. $\endgroup$
    – Oscar Bravo
    Nov 2, 2020 at 9:30

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