Just a little slice will do
by Bob Berman
May 13, 2010 01:00 AM | 0 0 comments | 4 4 recommendations | email to a friend | print
In this time of tight economics, perhaps it's time for a new hobby. Buying antique sports cars is great, and so is collecting Ming vases; but if you're on a budget,'s an idea: You've probably never heard of this practice, but millions around the world stalk the Moon. Astronomy journals periodically contain letters and articles catering to this odd-if-harmless practice; and if you're going to give it a try, now's the time.

Every sport has a way of doing business or keeping score. In chess it's points; in golf, strokes. With the Crescent Moon, the thing that matters is the age of the Moon. This is simply the time that has elapsed since it was New, or most in line with the Sun.

The idea is to try to spot the youngest (meaning thinnest) Crescent Moon possible. The trial is not just that a very young Moon is as slender as a hair, but that it is buried deep within the glow of twilight, not far from the Sun. Well, exact New Moon is Thursday evening, so let the clock start ticking.

Everyone agrees that a two-day-old Moon is easy to spot - and this is what we'll see on Saturday night. (Actually, if you're really going to get into this, the Moon will then be 46 hours old; those few hours make a difference.) It's generally also conceded that a Moon younger than about 14 hours is impossibly difficult. A 24-hour Moon is challenging, but often observed.

On Friday evening we'll see a 22-hour Moon. Friday will thus offer a decent challenge, while the Saturday-evening Moon should be very doable and gorgeous, while Sunday brings an in-your-face Moon.

Binoculars make it easier. The record with binoculars is 13 1/2 hours; nobody has yet been able to find a Moon younger than 15 hours without them.

Living in upstate New York, we find that the young Moon sits too deeply in twilight to make seeing any thin Moon possible except between February and early May. It's optimal right now because the Moon's path rises most vertically above the point of sunset. The current Crescent, then, is among the year's easiest. If you've got a nice flat unobstructed shot at sunset, you should be able to see the hair-thin Moon on Friday evening at 8:45.

But Saturday, that will be a knockout. At 9 p.m. - that's the time to look - you'll see a bright star above the Crescent. This is Venus, now returning after nearly a year's absence. If it's cloudy, check out the fatter three-day-old Moon on Sunday night, then with Venus below it.

Also look for Earthshine. That's the odd glow on the Moon's dark portion. This is pure Earthlight, bouncing from our planet to illuminate the sunless lunar hemisphere. Earthshine will be particularly bright on Friday and Saturday night.

This weekend also gives us the final smiling Crescents of the year. It's only a little tilted left, and nearly oriented with its horns straight up. After this, each month the evening Crescents will increasingly stand on their side, like archers' bows.

Yes, the thin young Crescent bestows a strange, ancient satisfaction. The smiling Moon makes you feel the same.

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