This meteor shower
is usually the year’s most reliable, but tonight the meteors will have to compete with the Moon, nearby and nearly at its brightest.
The moment of Full Moon is 0:06 Universal Time at the beginning of Dec. 14; which by American clocks is back in Dec. 13, 7 PM in the Eastern zone, 6 in the Central, 4 PM on the west coast.
The Moon when Full has to be near to what I call the anti-Sun point, and so is the radiant point of these meteors, which come inward across our orbit. That is why the radiant and most of the meteor trails spreading from it are in the sky just about all night, unlike those of meteor streams hitting us head on in the morning hours or overtaking us from behind in the evening.
The Geminids, unlike some showers which have sharp peaks, typically have a “plateau” of about 22 hours, during which the number of meteors seen per hour – in ideal conditions – may rise above 50, perhaps as high as 130.
My friend and meteor expert Alastair McBeath, who used to contribute the “Meteors” section for the Astronomical Calendar, recently wrote to me that “I noticed the 2016 IMO [International Meteor Organization] Shower Calendar didn’t give timings for the moonlit Geminid peak this year. So I did a couple of quick calculations,” and he found that:
The extended peak (plateau) should be from about Dec. 13, 7:30 UT, to Dec. 14, 5 UT.
And the main peak, Dec 14, 0:15 UT. (6 PM Central US time.)
One pleasant feature of the Geminids (the Astronomical Calendar 2016 section tells of others, such as the discovery of their origin from an asteroid, and their suitability for a “star vigil”) is that you can start seeing them soon after dark. I bet you’ll see at least a few through the moonlight.