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All Things Not Quite Equal

The equinox marks the start of autumn, but it isn’t quite 50/50 day and night

The moon waxes in the evening sky this week, with first-quarter occurring on the 22nd. That day has been dubbed
International Observe the Moon Night. Astronomers, educators and sky enthusiasts from around the world have set the date to encourage people to appreciate our only natural satellite. For teachers, students or the curious, log onto www.observethemoonnight.org for events, activities and moon-related topics. Or simply take a moment to gaze at this wonder, and give a wink in honor of Neil Armstrong.
    Saturday is also the autumnal equinox, when the sun hovers directly over earth’s equator at high noon, ushering in fall for us in the Northern Hemisphere. On this day, daylight and nighttime are evenly divided — well, almost.
    As you’ll notice with the times of sunrise and sunset below, they are closest to 12 hours apart Tuesday and Wednesday. This discrepancy is a result of how we measure sunrise and sunset. Sunrise occurs when the first edge of the sun’s disc crests the horizon, while sunset falls as the last of that disc sinks below the horizon — not when the disc’s center crosses either horizon. This adds a couple minutes of daylight, the size of the sun’s disc, to each day.
    Sunset reveals Mars in the southwest, with Saturn 20 degrees to the west and much closer to the horizon. They're now about 20 degrees apart. Shining a ruddy orange, Mars is slightly brighter than golden Saturn.
    Jupiter rises in the northeast before midnight, and as daybreak approaches the planet is high in the south. Look for the orange glow of Aldebaran, the eye of Taurus the bull, trailing Jupiter by less than 10 degrees.
    Venus rises around 3am and is ablaze high in the east come daybreak.