Earlier this week I wrote about the crescent moon passing near Venus tonight (Feb. 27). If you go out at dusk and look up in the southwestern sky you can’t miss it. Venus and the moon will be about 5 1/2 degrees apart all day today. Since most pairs of binoculars cover 5-7 degrees of sky, if you can find the moon before sunset, you can also see Venus in full daylight.
I always get a kick seeing the planet in a perfectly blue sky with the sun still up. You get a sense for its place in the solar system because you see both the planet and the star it orbits simultaneously. Why not give it a try? Face in the sun’s direction between 4 and 6 p.m., make a vertical fist and reach your arm to the sky. Then, mark off four-and-a-half fists to the upper left of the sun to find the pale lunar crescent.
Got it? Good. Point the binoculars at the moon and carefully focus until it’s nice and sharp. Then place the moon at the center left edge of the field of view and look for a tiny, bright point of light on the opposite side. That’s Venus! If you live in the eastern and central U.S. the planet will be near the 2 o’clock position around 5 p.m. Skywatchers on the West Coast will see it closer to the 3 o’clock spot. If you look say during mid-afternoon it will be more to the upper right.
A second challenge awaits. Once you’ve memorized the planet’s position in relation to the moon, lower the binoculars and try to see it without optical aid. Provided the sun is low it shouldn’t be too difficult. This is also the best time to observe Venus with a telescope because the bright sky tames the planet’s glare. In a dark sky it shimmers and dazzles. With a magnification of 75x or higher it will look like a pure white, miniature gibbous moon. White because Venus is under perpetual cloud cover, and clouds reflect sunlight well.
You might think that the white color indicates water vapor clouds like those on Earth, but they’re anything but. The clouds are composed of sulfur dioxide and droplets of sulfuric acid. Sulfur dioxide is responsible for the sharp, sulfury odor you smell when striking a match. Sulfuric acid is a corrosive liquid commonly found in car batteries. But these toxic substances sure look pretty from 84.5 million miles (1.36 million km) away, the distance that separates Venus from Earth today.