Early risers in North America are in for a treat on the morning of Wednesday, April 22nd, when the waning crescent Moon passes in front of the brilliant crescent Venus.For much of the continent the occultation happens after sunrise in broad daylight. If the air is clear you can find the thin, dim Moon about 33° to the upper right of the early-morning Sun, with Venus near its edge. Sadly, this event will be a near miss along the Eastern Seaboard.
I'm tempted to hop a westbound plane, because in the Far West the occultation happens during morning twilight — with the Moon and Venus shining beautifully before sunrise but very low above the eastern horizon. When the Moon covers Venus they'll be only 6° up as seen from Los Angeles, 4° from San Francisco, and 6° from Seattle. When Venus reappears at these locations the Moon will be about 10° higher, with the Sun already risen or nearly so.
Because the Moon is waning, its bright edge will be the one that covers Venus and its dark limb will uncover it, as shown in the diagram above. The thin crescent Moon will be only 9% sunlit, while Venus (40 times smaller) will be a 17% crescent.
At locations where the sky is still fairly dark, all you'll need are your eyes to watch this celestial spectacle. You'll probably need binoculars or a telescope where the sky is bright. Because of Venus's significant angular size, its disappearance and reappearance will each be gradual, taking 30 seconds or more.
You can gauge the approximate times of Venus's disappearance and reappearance at your site using the maps below. Interpolate between the red time lines to get the Universal Time of the event. Along the graze line, you'll see the Moon's southern limb skim Venus but never quite cover it. The maps also indicate whether your location will be in twilight or daylight at this time. (You can get customized predictions for several hundred cities and towns here.)
And if you're willing to get up a few hours earlier, you might be treated to a nice smattering of "shooting stars" from the annual Lyrid meteor shower. In most years you'll see fewer than 20 Lyrids per hour before the first light of dawn even under perfectly dark skies. But some years have brought outbursts of up to 90 per hour. Will 2009 be one of those?
Click here to check out the prospects for all of 2009's best meteor showers.