Sky Talk April 2009: Meeting of the Crescent Worlds

On the morning of April 22nd, the crescent Moon will sideswipe the crescent planet Venus in a spectacular pre-dawn show for portions of North America. Seen from the western two-thirds of the country, our lovely satellite will actually cover (or occult) the radiant planet, while those in the East will see a striking “near miss.”

If it’s clear where you are before dawn on April 22nd, plan to be outdoors looking toward the eastern horizon an hour before sunrise. In the western third of the country, you will find a very thin crescent Moon only two days from its New phase just to the right of brilliant Venus. As you watch, the lunar crescent will slowly approach the planet — and then occult it from view! For the central US this happens just after sunrise, while further east it will be seen as a fascinating close encounter before the brightening sky engulfs the two worlds and hides them from view to the unaided-eye.

In the West this event can be enjoyed with the naked-eye alone, while binoculars (the Celestron SkyMaster 7×50 glass being superb for the purpose -#30311-02 in the Edmund catalog) will greatly enhance the effect. Like those in the East, observers in the center of the country will see the Moon and Venus close together before sunrise. If you carefully continue to follow them in binoculars (tripod-mounted ones being recommended here) you should be able to see the actual occultation when it occurs since Venus is bright enough to be seen in broad daylight. (Note that in doing so, it’s critical that you don’t accidentally sweep into the blazing Sun itself while following the pair!) The best view of all no matter where you are will be through telescopes at magnifications of 30X or more, for they will clearly show Venus’ beautiful crescent shape. (Steadily-held or image-stabilized binoculars can also reveal it upon close inspection.) Even scopes as small as the Scientifics 60mm refractor (#30823-61) will offer a ringside seat for this spectacle where seen during twilight, and wide-field ones like the Edmund Astroscan (#30050-01) will show both worlds seemingly suspended in space (which, of course, they really are!) with lots of sky around them. When the Moon actually occults Venus, a definite sense of “three-dimensionality” will occur since the former is obviously closer to us than the latter!

For those in the West, the occultation itself is scheduled to happen just after 6:00 a.m. MDT, while along the West Coast it will occur around 5:00 a.m. PDT. As seen in a telescope, the bright lunar limb will slowly cover Venus’ much smaller crescent. There’s also an added bonus for those viewing this event along the West Coast — observers will be able to see Venus emerge from the Moon’s dark limb an hour later (still in a twilight sky) as our satellite completes its eastward swing across it.

–James Mullaney
Former assistant editor at Sky & Telescope magazine and author of five books on stargazing.

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