A pilgrimage to the Pen Henge standing stone array at the top of Munson Mountain will be held to mark the arrival of the Vernal Equinox on March 20.
The Pen Henge stones delineate the sunset points on the four cardinal dates of the year.
Anchored by the heel stone, the equinox stone points to the sun’s sunset point at both the spring and fall equinoxes. The other two stones mark the winter and summer solstice setting points, respectively.
As with previous events, members of the Okanagan Centre of the Royal Astronomical Society of Canada, RASC, welcome the public to join them for the observation which will mark the halfway point of the sun’s annual migration.
If clear skies permit on Wednesday, participants will be able to watch the shadow cast by the setting sun creep slowly from the equinox stone to align perfectly with the heel stone.
The Penticton gathering will begin around 6 p.m. in preparation for the actual sunset which will occur around 6:35 p.m..
The actual moment of the equinox will have taken place at 4:02 a.m. that morning.
Leading the observance will be OC RASC Penticton vice president Ryan Ranson who will be joined by other club members who will set up Sunspotter telescopes to allow solar viewing by the public.
The Pen Henge project was conceived in 2009 during the International Year of Astronomy by members of the society, which is now part of the OC RASC. The project was supported by the city council and parks supervisor Jeff Lynka.
“For most of the year the structure simply illustrates the enormous range along the western horizon where the sun sets. Most people subconsciously know of this, but they are quite fascinated to see the idea laid out so graphically,” said Chris Purton, a retired scientist at the Dominion Radio Astrophysical Observatory at White Lake, who spearheaded the Pen Henge project.
A brass plaque with a brief explanation of the array is permanently attached to the top of the heel stone.