11:32 am - Monday May 28, 2012

Astronomy Buffs Enjoy Long-Awaited ‘Venus Transit’


Transit-of-VenusEast Norriton: They came from far and wide to set up their telescopes, put on their safety glasses and keep their fingers crossed that Mother Nature would cooperate with fair skies on Tuesday evening.

The extraordinary event in the sky that captured their attention was the transit of Venus, which occurs when the planet named for the Roman goddess of love slips directly between Earth and the Sun.

The alignments happen in pairs that are eight years apart but separated by more than a century. The last one caught our well-protected collective eye back in 2004. Prior to that you had to go back to 1874 and 1882 for evidence of sightings.

No doubt about it, the heart of the universe for astronomers, historians and hobbyists on Tuesday evening was the onetime summer home of David Rittenhouse, renowned local astronomer, inventor, clockmaker, mathematician, surveyor, craftsman and first director of the U.S. Mint, who built the first telescope known to exist in the colonies. Rittenhouse observed the transit of Venus from his summer farm in what was then known simply as Norriton, now the campus of Valley Forge Medical Center and Hospital.

“This is the area where David Rittenhouse had his observatory, which was made of wood, in 1769,” noted Fred Jackes, assistant administrator Valley Forge Medical Center and avid historian.

The transit was as much an event in Rittenhouse’s time as it is today, he said. “This was a big deal in the 18th century because they wanted to have multiple observations of when Venus actually touched the sun’s disc and when it exited, and they were going to compare their observations in time.

“It was very important to time them scientifically and figure out where you were on earth in terms of latitude and longitude. And then they would work out by trigonometry the distance from the earth to the sun. For the 18th century this was big science.” Back then, astronomers from all over the world endured incredible adversity as they lugged around heavy equipment to places like India to observe the transits in 1761 and 1769.

“They actually got pretty good estimates, particularly for the 1769 one, but their instruments weren’t quite up to the mark,” Jackes said. “The first one was mostly not visible on the North American continent. For the 1769 transit, the American Philosophical Society in Philadelphia wanted to show they could do big science too and set up teams, and David Rittenhouse was a big part of that. He built his own observatory and made his own instruments.”

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