                        Astronomy Picture of the Day

    Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                                2021 July 11

                                Find the Moon
    Image Credit & Copyright: Jimmy Westlake (Colorado Mountain College)

   Explanation: Where's the Moon? Somewhere in this image, the Earth's
   Moon is hiding. The entire Moon is visible, in its completely full
   phase, in plain sight. Even the photographer's keen eye couldn't find
   it even though he knew exactly where to look -- only the long exposure
   of his camera picked it up -- barely. Although by now you might be
   congratulating yourself on finding it, why was it so difficult to see?
   For one reason, this photograph was taken during a total lunar eclipse,
   when the Earth's shadow made the Moon much dimmer than a normal full
   Moon. For another, the image, taken in Colorado, USA, was captured just
   before sunrise. With the Moon on the exact opposite side of the sky
   from the Sun, this meant that the Sun was just below the horizon, but
   still slightly illuminating the sky. Last, as the Moon was only about
   two degrees above the horizon, the large volume of air between the
   camera and the horizon scattered a lot of light away from the
   background Moon. Twelve minutes after this image was acquired in 2012,
   the Sun peeked over the horizon and the Moon set.

                 Tomorrow's picture: comet, planet, or star?
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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