Exact First Quarter Moon
Taken by Peter Lowenstein on July 30, 2017 @ Mutare, Zimbabwe
Click photo for larger image
  Camera Used: Panasonic DMC-TZ60
Exposure Time: 10/1250
Aperture: f/6.4
ISO: 250
Date Taken: 2017:07:30 20:38:39
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The First Quarter Moon on 30 July 2017 occurred at 15.23 UT. The first photograph was taken from Mutare at exactly that time (17.23 LT). The terminator is straight and it is showing a lighted hemisphere (half-moon) to Earth. The following animation confirms that if this is compared with a Fourmilab simulation of the Earth as viewed from the Moon at the same time, modified from http://earthsky.org/moon-phases/first-quarter, the illumination on the First Quarter Moon viewed from Earth is the same as that on the Last Quarter Earth viewed from the Moon. The photograph was taken using a Panasonic Lumix DMC-TZ60 camera in sunset scene mode with a combined optical+digital magnification of x100.
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I think you failed to take into account that the illuminated face of the first quarter moon is to the right for observers at mid-northern latitudes, and the complementary third-quarter earth would be facing left as viewed from the mid-northern moon -- just as the linked EarthSky page shows them.

At your mid-southern location on earth (youre upside down from our mid-northern perspective), the first-quarter moon is, of course, illuminated on the left, and upside down too (compare it to the image at EarthSky, yours is ultimately rotated 180° compared to theirs). Therefore, your complementary third-quarter earth should be viewed from the mid-southern moon and then the upside down earth would be illuminated on the right (like the moon, it would be rotated 180°). Also, when superimposed on each other, the terminators of the earth and moon would not coincide, but be a shallow X pattern.
Posted by JoeStieber 2017-08-01 14:18:27
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