Our July meeting, originally scheduled for the 9th, was moved to the 16th because President John Bell was under the weather.  And on the 16th, the eye of Hurricane Claudette was directly overhead, with its heavy attendant rains, so we rescheduled our meeting for July 23.  Unfortunately, that evening found us conflicting with a presentation by John Karges on ecology.  Some of our members found it hard to be in two places at the same time so our attendance was down to 12 people.
           John Bell presented a video entitled Destination Mars, on the requirements of a manned expedition to the red planet, and a safe return.  Because of the lateness of the hour at the end of the video, and because we had no pressing issues, we did not hold a business meeting.

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           By way of introduction, John noted that the British now have an unmanned space probe on its way to Mars.  The probe is appropriately named the Beagle, after the ship that carried Darwin’s expedition around the world.
           John also mentioned Project Orion, involving atomic scientists who had worked on the a-bomb program during World War II.  The Orion rocket was to be nuclear powered.  It would have weighed 4,000 tons  and would have carried a payload of 1,000 tons to Mars.  But the project was soon abandoned because of concerns about safety.  However, NASA is now interested in Orion as a possible means of diverting an asteroid headed for the earth.
           The video Destination Mars considered a manned mission that would travel 250 million miles over a period of 2 1/2 years.  Mars is only about 1/3 the size of Earth, but there are mountains 3 times the size of Everest.  Mars gravity is only 1/2 that of the Earth.  We already know something about the geology of Mars because meteorites blasted off its surface by impacts have been found on the earth.
           Mars has caught the world’s imagination for many years, due in no small part to Percival Lowell’s belief that the planet was criss-crossed by a network of canals to bring water from the polar snowcaps to the desiccated equatorial regions.  But Lowell’s canals have long since failed to appear in our many close-up pictures of the planet.  There are, however, many photographs of channels that give strong evidence of flowing water, perhaps long in the past.  Indeed, if all the ice on Mars melted, the planet would be covered by 600 feet of water (the earth, however, would be under 6,000 feet if all our water melted).
           Former Astronauts Eugene Cernan and Buzz Aldrin discussed plans for a manned expedition to Mars.  One of the most difficult problems involves the huge weight of the rocket fuel to be consumed on a trip to Mars and back.  One possible solution is to send rockets to Mars that would manufacture the fuel needed for the return trip, producing methane and extracting oxygen from the abundant carbon dioxide in the Martian atmosphere.  Because of safety concerns, nuclear rockets have been essentially ruled out.  (See Sky Watch for more on Mars.)

           The Perseids are perhaps the best known meteor shower to serious observers and the general populace alike.  Every year we await its arrival, its distinctive meteors, and the nice warm nights of summer.
           This famous shower has been observed for about 2000 years, with the first known information on these meteors coming from the far east.  In early Europe, the Perseids came to be known as the Tears of St. Lawrence.  In an article by Mark Littmann called 'The Discovery of the Perseid Meteors' on the Sky and Telescope website, Littmann writes: "Saint Lawrence was tortured and killed in Rome on August 10, 258 during the reign of the anti-Christian emperor Valerian. . .  Citing Quetelet, 'a superstition has 'for ages' existed among the Catholics of some parts of England and Germany that the burning tears of St. Lawrence are seen in the sky on the night of the 10th of August, this day being the anniversary of his martyrdom.' "
           Legends abound about Perseus.  In ancient Greek mythology, he was a hero - the son of Zeus.  On one quest, he took off to slay the famed Medusa, a beautiful mortal lady who had been unceremoniously turned into a fearsome Gorgon by the jealous goddess Athena.  Medusa's beautiful hair became a squirming mass of snakes - and her gaze deadly.  Perseus travelled with the help of winged sandals from Hermes, the messenger god; a sword of diamond from Hephaestus, the god of fire and the forge; and a  magical helmet to make him invisible, from Hades, god of the underworld.  He slew Medusa without looking at her by using her reflection in his shield.  The blood of Medusa fell to earth and created the great winged horse Pegasus.
           On his way home, Perseus rescued the princess Andromeda, daughter of King Cepheus, who was chained to a rock as a sacrifice to the sea monster Cetus because of the vainful boasting of her mother, Queen Cassiopeia.  Perseus rescued the fair maiden and married her.  And now, in our constellations, we have all the players in the legend: Perseus, Pegasus, Andromeda, Cepheus, Cassiopeia, and Cetus - and even the infamous Medusa, immortalized as the 'Demon Star' in the constellation of Perseus.
           The parent comet of the Perseid meteors, 109/P Swift-Tuttle, was discovered in July of 1862 by both Lewis Swift of Marathon, New York, and Horace Tuttle of Harvard Observatory, Massachusetts.  It was about magnitude 7.5 at discovery and brightened to about magnitude 2 by early September, which is about the same brightness as the stars in the Big Dipper.  It sported a tail of between 25 and 30 degrees long, and was quite impressive.  By length comparison, the pointer stars of the Big Dipper are about 5 degrees apart. The comet comes around to our part of the solar system about every 120 years and was seen most recently in the mid 1990's. In November of 1992, it brightened to about magnitude 5.0.
           Because the orbit of the Perseid meteoroid particles is tilted so much in relation to the plane of our own solar system, the Perseids have stayed fairly similar in characteristics since ancient times, and have not been changed much by the influence of our large planets such as Jupiter.  It was Schiaparelli, the astronomer most noted for observing the so-called 'canali' on Mars, who discovered that the Perseid meteors were related to Comet 1862 III, also known as 109/P Swift-Tuttle.  This was the first proven association between a comet and a meteor shower. 
           The magnitude or brightness of the meteors themselves is interesting as well. Studies by Hruska and Ceplecha in the 1950's indicated that the Perseids generally seem to be brighter before the date of maximum activity than afterwards, but that some periods of brighter or fainter meteors do occur. This tends to indicate some filamentary structure in the Perseid meteoroid stream.  In other words, we encounter  clumps of brighter or fainter meteors as the earth passes through different layers of debris shed long-ago by Comet Swift-Tuttle.  These are fast meteors, at about 59 km per second.
           The Perseids (PER) can be seen from about July 17th until about August 24th, with the main peak time occurring on the 13th of August at 4h 40m UT (Universal Time).  ZHR rates at maximum reach about 110 meteors per hour.  ZHR stands for Zenithal Hourly Rate, and is the average number of meteors that observers would expect to see if they were out under a dark country sky, and if the radiant, the area in the sky where the meteors seem to come from, were directly overhead.
           Will we see this many meteors for this Perseid display?  Looking at the calendar, the full moon in August occurs on the 12th, at 4h 48m UT.  This will wash out the fainter meteors.  However, the good news is that the Perseids are noted for lots of bright meteors, and these will still be visible.
           How can you see more meteors, in spite of the full moon this year?  It is still worthwhile getting away from city lights.  Face away from the moon when observing - put it behind you, or at the very least, to your side.  Do not stare at it, or it will destroy whatever dark adaptation you have.  Or try blocking the moon with a tree, or even a dark umbrella that you reposition during the night.  Every little bit of decreased light or glare will increase your meteor perception.
           The Perseids are probably the best shower of the year to try photographing.  It's warm, and the number of bright meteors is high.  Use a camera with a time exposure, and a normal lens (not a telephoto).  Set the lens wide open (or perhaps 1 stop down), and set the focus on infinity.  Put the camera on a tripod, and use a cable release to keep the lens open.  You won't want fast film - or it will 'fog' over quickly with the bright moon.  Use a slower film, and keep your exposures fairly short - you might try 5 minute shots, for example.  It is always wise to take a variety of exposures, as some will turn out better than others.
           A map showing the radiant of the Perseid shower, and its movement across the sky throughout the month, can be found on the website of the IMO, the International Meteor Organization, at http://www.imo.net/calendar/cal02.html#Perseids
           Is there just one peak time?  In fact, there are several.  The predicted times of high Perseid activity are as follows, according to the IMO's 2003 Meteor Shower Calendar:  Aug 13, 4h 40m UT - the main peak;  Aug 13, about 2h 40m UT - possible maxima;  Aug 13, about 14h 40m UT - possible maxima.  For Central Daylight Times, subtract 5 hours from the above.  Good hunting!