Here's what I wrote for the NAMN. It's a bit technical, so feel free to ask any questions, and I'll also try and write a more casual observer version later today.
1. (GEM) Moon Free Geminids Highlight the Month
Another major shower meets the New Moon….almost. Technically, it occurs about 2 days after the Geminid peak, but since there are so many dark hours near the winter solstice, there will be plenty of time for anyone who wants to watch, and the thin crescent moon won’t be a problem anyway. The month is bracketed by two Full Moons, on the 2nd and 31st, which leaves the first week with lengthening evening hours, and the last week with waning morning hours without that big bulb in the sky.
The IMO gives the GEM peak time at Solar Longitude 262.2, or 0510 UT Dec 14 (midnight EST, 9PM Nov 13 PST) +/- 2.3 hours. Video data published in WGN 37:4 by Sirko Molau places the peak over the last decade or so at Solar Longitude 261.5, or about 1200 UT on the 13th. Each is supported by IMO preliminary visual data for the last few years, which has shown multiple peaks occurring between about 261.4 and 262.4. This would mean the best times would be the early morning of the 13th, and the entire night of the 13/14th for North America.
The video data shows a start date of Dec. 4th, a few days earlier than the standard IMO start date of the 7th. The shower ends crisply on the 17th using both sources.
In the Northern Hemisphere, where the nights are the longest the radiant rises a bit after sunset, and sets a few hours after sunrise. In the Southern Hemisphere, while the radiant rises later, since the sun sets later as well, most of the observing window is dark. No matter where you are, the radiant reaches its maximum elevation (transit) close to 2 AM local time, almost perfect for a long night of meteor viewing. With the projected peak between midnight and 2 AM for the EST time zone, the best rates could occur along the east coast, but even in the west, the radiant will be at least 30 degrees above the horizon (producing rates about half of the ZHR under very dark skies) with the rising radiant compensating for the falling ZHR. Remember, though, showers can always provide surprises in timing and rates; the only way to now for sure is to watch!
The radiant is not far from Castor (actually a bit to the west near +4.2 magnitude rho Gem) so is easy to find. The Geminids are also an excellent shower for photographic methods. The slower velocity (about 35 km/sec compared to Leonid speeds twice as fast) allows more photons to fall on a given piece of film or on the CCD pixels, and the much higher rate for North America should give plenty more opportunities to capture one.
1. (GEM) Moon Free Geminids Highlight the Month
Another major shower meets the New Moon….almost. Technically, it occurs about 2 days after the Geminid peak, but since there are so many dark hours near the winter solstice, there will be plenty of time for anyone who wants to watch, and the thin crescent moon won’t be a problem anyway. The month is bracketed by two Full Moons, on the 2nd and 31st, which leaves the first week with lengthening evening hours, and the last week with waning morning hours without that big bulb in the sky.
The IMO gives the GEM peak time at Solar Longitude 262.2, or 0510 UT Dec 14 (midnight EST, 9PM Nov 13 PST) +/- 2.3 hours. Video data published in WGN 37:4 by Sirko Molau places the peak over the last decade or so at Solar Longitude 261.5, or about 1200 UT on the 13th. Each is supported by IMO preliminary visual data for the last few years, which has shown multiple peaks occurring between about 261.4 and 262.4. This would mean the best times would be the early morning of the 13th, and the entire night of the 13/14th for North America.
The video data shows a start date of Dec. 4th, a few days earlier than the standard IMO start date of the 7th. The shower ends crisply on the 17th using both sources.
In the Northern Hemisphere, where the nights are the longest the radiant rises a bit after sunset, and sets a few hours after sunrise. In the Southern Hemisphere, while the radiant rises later, since the sun sets later as well, most of the observing window is dark. No matter where you are, the radiant reaches its maximum elevation (transit) close to 2 AM local time, almost perfect for a long night of meteor viewing. With the projected peak between midnight and 2 AM for the EST time zone, the best rates could occur along the east coast, but even in the west, the radiant will be at least 30 degrees above the horizon (producing rates about half of the ZHR under very dark skies) with the rising radiant compensating for the falling ZHR. Remember, though, showers can always provide surprises in timing and rates; the only way to now for sure is to watch!
The radiant is not far from Castor (actually a bit to the west near +4.2 magnitude rho Gem) so is easy to find. The Geminids are also an excellent shower for photographic methods. The slower velocity (about 35 km/sec compared to Leonid speeds twice as fast) allows more photons to fall on a given piece of film or on the CCD pixels, and the much higher rate for North America should give plenty more opportunities to capture one.
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