Friday, September 22, 2006

Like a druid drawn to Stonehenge

The autumnal equinox occurs tommorow,Sept. 23, 2006, at 12:03 A.M. EDT. However, that did not stop me, and many others, from stopping by the steel Sun Triangle to consider our local solar noon event as an indication of equinox. The large steel sculpture is a product of Athelstan Spilhaus (checkout the clock he designed) in the pit of the McGraw Hill Building in NYC. I arrived around twenty minutes to one and a dozen or more people were gathered by five to one, already past the local noon. And just like the solstice event earlier this year, people lined up to look directly at the sun with no protection other than some heavy squinting. For the equinox one sights along the long, top side of the triangle as opposed to the forward short side.

Charlie has a photograph he marked up showing how the sides are used with these seasonal events and has a lot of good shots & description on this page.

I thought that noon occurred at 12:50pm EDT because that's when I considered the shadow shortest. The shadow is not as crisp as I'd like it and would even say that noon occurred at 12:51 when I saw a small "notch in the shadow" that could only be seen if sunlight was aligned with it. The "notch" is created by the joint between the triangle and its base.

When the Sun does cross the celestial equator from north to south, marking of the beginning of Fall, it will be noon somewhere in the world. As someone said while pointing at the Sun Triangle, "But they don't have this."

This is an old photo of the Sun Triangle taken at the time of solstice. I forgot my camera today but Charlie had his. Stop by his blog later to see what he uploadedhis report. Compare the shadows from solstice with Charlie's photos of equinox relative to the base of the gnomon.