Friday, 10 August 2012

The Perseids - Tonight is the night!

I have been interested in astronomy for as long as I can remember. At one time I used to teach astronomy. However, this interest also filtered into another hobby that I had which is amateur radio. Whenever a meteor burns up in the atmosphere it leaves behind a trail of ionised gas in it's wake. This ionisation trail can reflect signals in the VHF frequency band. I used to experiment in bouncing signals over long distances off the meteor trails. The August Perseids is a very prolific meteor shower. 

The number of meteors in an hour is known as the ZHR rate. (Zenithal Hourly Rate) The Perseids can have very high ZHR rates. The meteors are associated with the comet Swift-Tuttle.  The stream of debris which creates the meteors is called the Perseid cloud and stretches along the orbit of the comet. The Earth on its orbit passes through the debris trail each year.

The peak in activity being between August 9 and 14 each year.  During the peak, the rate of meteors often reaches 60 or more per hour. They can be seen all across the sky, but because of the path of Swift-Tuttle's orbit, Perseids are primarily visible in the northern hemisphere. As with all meteor showers, the rate is greatest in the pre-dawn hours. The weather tonight and tomorrow promises to be good enough to make observations worthwhile.

As of early morning on August 10, 2012, the zenithal hourly rate (ZHR) of meteors visible in a dark sky has gone up to 42! That’s according to the International Meteor Organization. It’s time to watch meteors! The peak mornings for the annual Perseid meteor shower will be August 11, 12 and 13, but clearly any time now is good.

August 12 might be the best morning. August 11 might be better than August 13. The moon is waning now. The Delta Aquarid and Perseid meteor showers combine in late July and August to create what most consider the best and most reliable meteor display for Northern Hemisphere observers. As always, after midnight is the best time for meteor-watching. The moon will be there, but getting thinner.

Find a dark, open sky far away from the harsh glare of city lights, lie down comfortably on a reclining lawn chair and enjoy the show. You don’t need to know the constellations. You don’t need special equipment. Simply look up to watch Perseid meteors streaking the night time sky. Look towards the North East night sky for best effect.


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