Sunlight on Pluto is only a thousandth as strong as it is here on Earth. With careful timing, you can experience what it'd be like to stand on Pluto at noon.
Right now Pluto is 31.94 astronomical units from the Sun. This means that the summery sunlight here in Boston is about 1,000 times more intense (31.94 × 31.94) than it is on Pluto. And while 1⁄1,000 of a Sun might seem very dim, it really isn't. Consider: instead of the Sun's dazzling apparent magnitude of –26.7, as we see it, Plutonians would still see our star as magnitude –19.2. That's more than 400 times brighter than the full Moon.
For the scientists and engineers managing the New Horizons spacecraft, now less than a month from its history-making flyby of Pluto, accounting for this reduced lighting is just a matter of taking somewhat longer exposures. (It's not quite that simple: the lighting will vary across the globe, and there'll be differences for surfaces that are intrinsically bright or dark.) Still, when all this gets factored in, out pops a set of exposure times that should prove reliable.
For us humans, however, it's more complicated to imagine what we'd experience standing on Pluto. For example, the atmosphere is so tenuous that it would scatter very little light around you. Recall the stark shadows that Apollo astronauts experienced while on the Moon. Yet sunlit portions of the lunar landscape still looked very bright to them.
While it's difficult to imagine what 400 full Moons in the sky, we can get a sense of what midday on Pluto might be like using twilight. It turns out that the sky's total brightness is a good match for "Pluto time" when the Sun is about 1½° below the horizon. This occurs, depending on your latitude, about 8 to 10 minutes before sunrise or after sunset. Of course, it's hardly "dark" at those times! If you were to stand outside then, you'd have no trouble finding your way along a path or reading the July issue of Sky & Telescope (which features Emily Lakdawalla's preview of the New Horizons flyby).
So try experiencing "Pluto time" for yourself. You don't even need to do the calculation — the wizards at NASA have taken care of that for you with a handy online app. My next opportunity is 8:28 p.m. tonight — when's yours?
Want more background about Pluto and New Horizons' upcoming flyby? Check out the half-hour-long presentation I gave at the NorthEast Astronomy Forum (NEAF) in April.