Before sunrise on Monday – December 7, 2015 – people around the world will see the brightest and second-brightest celestial bodies of nighttime, the moon and Venus, shining close together during the predawn and dawn hours. The view from North America, Central America and the Caribbean will be especially spectacular, as the two brilliant beauties brush up together on the great dome of sky. From some parts of North America at Monday’s predawn, the moon will pass in front of Venus. Astronomers call this an occultation. The occultation is visible from the continental U.S., but only in daylight. However, December 7 also presents a great time to try to see Venus in the daytime, either with binoculars or your unaided eye.
John Ashley in Montana submitted the photo above to EarthSky. It’s a daylight occultation of Venus in August, 2000. He said it’s a composite of six photos taken at 1-minute intervals, photographed from Glacier National Park, Montana. It’s one of 100+ photos from his book, Glacier National Park After Dark, by the way. Used with permission. View it larger.
Follow the links below to learn more:
Predawn occultation of Venus on December 7. The most enviable location for watching a predawn occultation of Venus on Monday, December 7, is from northwestern North America (Alaska, Yukon, British Columbia and the Northwest Territories). People from that part of the globe can watch as the moon occults – covers over – Venus for an hour or more before sunrise.
Venus will disappear behind the lit side of the waning crescent moon and then reappear on the unilluminated side of the crescent.
We give the occultation times for three localities in local time below:
Occultation begins: 6:43 a.m. Alaska Standard Time (AKST)
Occultation ends: 7:50 a.m. AKST
Sunrise: 10:33 a.m. AKST
Occultation begins: 6:34 a.m. AKST
Occultation ends: 7:47 a.m. AKST
Sunrise: 9:56 a.m. AKST
Dawson, Yukon, Canada
Occultation begins: 7:50 a.m. Pacific Standard Time (PST)
Occultation ends: 8:55 a.m. PST
Sunrise: 10:48 a.m. PST
More information on the lunar occultation of Venus on December 7 is available right here. However, you must convert Universal Time to your local clock time. Subtract 9 hours from Universal Time for Alaska Standard Time (AKST) and subtract 8 hours for Pacific Standard Time (PST).
Daytime occultation of Venus on December 7. Virtually all of North America, Central America and the Caribbean will be in position to see the occultation of Venus on Monday, December 7. For the most part, though, this occultation will be during the daylight hours. If you can manage it, a daylight occultation of Venus is an excellent time to capture dramatic photographs, like the one at the top of this page by John Ashley, and like those caught by Ravindra Aradhya in Bangalore, India during the February 26, 2014 daytime occultation of Venus by the moon as seen from that part of the world.
Here are occultation times on December 7, for a few U.S. cities. Remember, Venus is disappearing behind the moon’s bright limb, and reappearing from its dark limb. The most stunning observation will be of Venus’ reappearance as the occultation ends. The reappearance is more difficult to catch, though!
Los Angeles, California
Occultation begins: 8:03 a.m. Pacific Standard Time (PST)
Occultation ends: 9:53 a.m. PST
Occultation begins: 9:35 a.m. Mountain Standard Time (MST)
Occultation ends: 11:12 a.m. MST
Occultation begins: 11:17 a.m. Central Standard Time (CST)
Occultation ends: 12:32 p.m. CST
Occultation begins: 12:42 p.m. Eastern Standard Time (EST)
Occultation ends: 1:46 p.m. EST
It’s true. People with good vision are able to see Venus in a daytime sky with no optical aid whatsoever. Most of us, though, will probably need binoculars spot Venus next the moon during the daylight hours on December 7. Just be sure to check the times listed above for the occultation! If you look, and can’t see Venus, it might be because the occultation is in progress, and Venus is behind the moon.
It might be tricky locating this very thin waning moon in a daytime sky. The best way is to follow the moon and Venus after the sun rises, checking on them from time to time to see if you can still spot them. Remember that the moon is west (right) of the sun; that is, from the sun’s location in the sky, you would track along the sun’s path, in a westward direction or direction toward the sunset point, to find the moon. The moon goes westward during the day, pretty much staying the same angular distance west of the sun all day long.
It may be helpful to block out the sun behind a building, or your hand, when seeking for the slender crescent. Keep in mind that the moon and Venus will be about 40o west (right) of the daytime sun. For reference, your fist at an arm length approximates 10o of sky.
Bottom line: Whether you’re in a position to witness the lunar occultation of Venus – or not – we highly recommend that you watch the great moon and Venus drama before sunrise on Monday, December 7, 2015!