By Geoff Gaherty
Starry Night Education

The Orionid meteor shower, one of the biggest and brightest of the year, is at its peak Wednesday morning, Oct. 21.

Skywatchers with dark skies and good weather could see a shooting star every 5 to 10 minutes, with brief bouts that might prove busier.

The Orionids, like most meteor showers, are caused by particles associated with a comet, in this case, the famous Halley's Comet. If you can't wait until Halley's Comet makes its next appearance in 2062, this is your chance to see a piece of it as it flies across the sky and vaporizes in Earth's upper atmosphere.

While most annual meteor showers are pretty minor events for the casual observer, the Orionids are one of the two or three best in the year, especially as this year there will be no moon to interfere with seeing the fainter meteors.

The Orionids typically produce about 15 to 20 meteors per hour at their peak, for skywatchers with dark skies. Expect an additional five to 10 sporadic meteors per hour — those not related to the shower. Urban and suburban residents will see far fewer, however, due to local light pollution.

Although you can probably see a few of the brighter meteors just about anywhere, weather permitting, a trip to dark skies free of light pollution will reward you with many fainter meteors. The other trick with all meteor observing is to wait until after local midnight to start observing. By then the radiant, the point in the sky from which the meteors appear to come, will be high overhead.

Be sure to dress warmly, as it will be chilly.

A bit more about the radiant: When you look into the radiant, you are actually looking directly at the point from which all the meteors are coming. In the case of the Orionids, this is a point just over Orion's left shoulder, close to where he's holding his club, and just between the feet of the Gemini twins. You're looking directly into the orbital path of Halley's Comet.

When you're actually observing, you don't need to know exactly where the radiant is, or look directly at it, as the meteors can appear anywhere in the sky, radiating out collectively like spokes from the hub of a wheel. In fact the longest and fastest meteors will be about 90 degrees away from the radiant.

The Earth passes through the orbit of Halley's Comet twice each year, the other time being May 6. There is a weak meteor shower associated with this date, the Eta Aquarids, but it is nowhere near as spectacular as this week's Orionids.

You can start to watch for this shower late Tuesday night, heading into Wednesday morning. But don't expect the evening session to be as fruitful as the early morning viewing. The shower's maximum activity — from the heart of the cosmic debris stream — will occur at 6 a.m. EDT Wednesday, just before dawn in eastern North America. So the best viewing times will be just before dawn in the eastern part of the country, and around 3 a.m. out West.

http://www.space.com/spacewatch/091016-gaherty-orionid.html