Tuesday, March 1, 2016

The March Sky and Tonight's Sky for March 1: Third Quarter Moon

With the month of March upon us, the lengthening of the days will be at its most noticeable as the Sun moves fastest near the equinox, which occurs on the 20th of the month. Besides the rapidly shortening nights thanks to the lengthening of the day, another dramatic loss in dark sky time will come on the second Sunday of the month (the 13th), which is when Daylight Savings Time returns. Needless to say, by month's end, there will be far less opportunity for observing as nightfall will come a lot later than it did at the start of the month. However, at least for a short while, there will be an extended window for morning observing with an extra hour of darkness at the start of the day.

Cool Constellations
At the start of March, the first order of business should be getting a last look at the winter constellations under dark sky conditions as, with the advent of DST, most will be low in the Southwest come nightfall and, unless one has a good horizon, too low to observe very well. The early-month, early-evening observing list should include Cassiopeia, Cepheus, Perseus, Orion, Canis Major, and Canis Minor. A few other winter constellations, including Auriga, Taurus, Gemini, and the Pleiades are still reasonably well-placed, though. As Orion was to winter, the Big Dipper is to spring in that it is a signpost to the stars. Starting at the Dipper, follow the arc of the Dipper to bright orange Arcturus, alpha Bootes, and the brightest star in the spring sky. To the left of the kite-shaped Bootes, look for the arc of stars that is Corona, the crown. Next, speed onto blue Spica, alpha Virgo, and one of the brightest spring stars. Next, continue the curve to trapezoidal constellation Corvus, the crow. Finally, conclude in dim Crater the cup. Moving higher in the sky, zodiac constellations Cancer and Leo are well-placed as well. Speaking of Cancer, look just below the cosmic crab for a distinct ring of stars, the head of Hydra, the sky's biggest constellation, which snakes (sorry) through over 120 degrees of sky. For those who like to stay up late (or get up extremely early), there's mythological strongman Hercules and the Summer Triangle high overhead and, to the South, Ophiuchus, Serpens, and Scorpius

Planetary Perceptions
On the planet front, you'll need to be an early bird to catch 4 of the 5 naked eye planets. The one exception: Jupiter, which reaches opposition on March 8. What does this mean? As seen from Earth, Jupiter is opposite the Sun in the sky, meaning that Jupiter is up all night from sunset to sunrise. Moving into the night, Mars is next to break the horizon, albeit in middle of the night, followed by Saturn. An item of note: Mars is clearly converging with Saturn as Saturn was rising about 2 hours after the Red Planet at the start of March but, by month's end, they will be rising within 45 minutes of each other. As an interesting note, the Moon will make a pair of close passes of these two planets, on the mornings of the first and 29th. Try and see both events as one will clearly be able to see how much closer the planets are with the Moon in the picture. Moving to the immediate predawn sky, Venus hangs very close to the predawn Eastern horizon all month. As for speedy Mercury, it will disappear from the morning sky early month before making a sudden reappearance as an evening object the last week of March as it heads toward its best evening appearance of the year in mid April. Last but not least, there's a true Young Moon (under 24 hours past New) visible at dusk on the 9th.

Tonight's Sky for March 1: Third Quarter Moon

Today, the Moon, second brightest object in the sky, has reached the Third Quarter phase, which means that it is exactly 270 degrees around its orbit of Earth.

As for lunar mechanics, the Moon is always half lit. The reason we don't always see it as such is thanks to orientation in relation to us. Right now, with the Moon at a 90 degree angle relative to the Earth and Sun, we see the Moon as half lit and half dark, leading to the popular, erroneous phrase 'half Moon.'

After today, we will see less and less of the Moon as its lit side turns more away from us and heads toward a new lunar cycle. 

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