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I live in NYC and just experienced the eclipse. What fascinated me the most was that despite the fact that the sun was about 70% blocked, the area was not noticeably dimmer. If the news wasn't saying there was a solar eclipse I wouldn't have realized it was happening.

How much of the sun needs to be blocked by the moon in order to noticeably dim an area?

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    $\begingroup$ As en.wikipedia.org/wiki/Lux#Illuminance notes, direct sunlight is about 100,000 lux, but even 10,000 lux is considered daylight. So, at 90% coverage, you may start noticing it's getting dimmer. Or you may just think it's clouds. You have to get over 99% coverage before it starts getting darker than an overcast day. $\endgroup$
    – user21
    Commented Aug 21, 2017 at 19:52
  • $\begingroup$ Not an exact duplicate, but your answer can be found under this more recent question: astronomy.stackexchange.com/questions/22234/… $\endgroup$
    – user1569
    Commented Aug 23, 2017 at 15:12

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Based on the CNN's reporting it appeared to get noticeably darker at near 95% coverage. That's just from watching the onset of darkness for locations experiencing totality.

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