Thursday August 16th Venus reaches the point in its orbit called greatest eastern elongation. As this graphic shows an inner planet, Venus or Mercury, is more or less at a right angle (90o) from the Sun and Earth at eastern elongation. From the surface of the Earth, your backyard, for example, Venus is to the left, or eastern side of the Sun and is setting after the Sun.
At eastern elongation the angle between Venus and the Sun is at its greatest, which for this elongation Venus will be 45.9o from the Sun. In terms of viewing Venus, this is as about as late as Venus will set, about 4 hours after sunset local time, meaning for some Venus may set close to midnight local time. This animated graphic shows Venus at sunset, then with Venus’s orbit shown, and then with the horizon removed to see where the Sun is relative to Venus.
From eastern elongation forward Venus will be moving westward toward the Sun, and each day setting closer and closer to the time of sunset. By October Venus will have orbited to inferior conjunction – between the Earth and the Sun. During this part of the inner planet orbit, from eastern elongation to inferior conjunction, the distance from Earth decreases and the apparent size of Venus increases. Venus also goes through phase changes much like our Moon, and so from eastern elongation to inferior conjunction Venus wanes from a small appearing gibbous phase to an increasingly thinner crescent phase.
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