SOLAR CALENDAR

This is an overhead view of the yard just south of the house. The large rock on the left is the Shadow Rock; the one on the right is the Equinox Rock; the one at the top is the Winter Solstice Rock. They weigh 100-200 pounds each, and were muscled into position after setting up the alignments using basic geometry. The Shadow Rock required a backhoe to properly position. If you construct the angle between these rocks you get 28º, the tilt of the Earth plus a 5º correction factor for our latitude.

It's tough to shoot both the Sun and the landscape in a single image without under- or over-exposing something, but this one worked out alright after masking the sky and tweaking the gamma. The disc of the Sun has been painted into the image at the origin of the visible rays — the actual Sun was behind that cloud. Sunset on the Winter Solstice is at azimuth 242º, 28º south of west, what some would call "WSW." This view is from the Shadow Rock looking toward the Solstice Rock.

Most people notice the days getting shorter as winter approaches, but few (other than astronomers) pause to think about why this happens. Sunrise on this date is 28º south of east. These far-south sunrise and sunset points cause the Sun to take a lower path through the sky compared to other seasons. The result is only 146º of the 360º ecliptic (path of the Sun) is visible. This in turn results in 9 hours 45 minutes of daylight. On the Equinox, for comparison, the Sun rises exactly East, sets exactly West, 180º of ecliptic are visible, and there are 12 hours of daylight.

After taking the above image, I reversed the view and shot back toward the Shadow Rock. You can see the alignment is right on. This was a fairly bright sunset for the Winter Solstice, with good contrast and sharp shadows. Just before the Sun dropped below the mountains it emerged from behind the cloud that hid it in the above image. Less than a minute after this image was captured the direct rays were gone.

Twice each year this shadow alignment occurs. The Equinox Rock, slightly out of picture to right, casts its eclipse on the Shadow Rock, as you can clearly see. To get these pictures I need to have a clear sunset happening on the correct date. It doesn't always all come together like this ... this was a good one. It's even tougher on the Winter Solstice, which took three years to get due to the usually cloudier weather on that date.

This was really spooky. Because the Sun sets so far north on this date (azimuth 298º in AZ) the house was in the way, and I never even attempted to set up an Summer Solstice Rock. Then, on a clear solstice sunset a few years ago, I noticed that the southwest corner of the house cast its own shadow on the Shadow Rock. Because of the longer distance to the house the shadow on the rock is too diffuse to capture on film, but the eyes can see it. So instead of trying to capture the shadow I just reversed the frame of reference. What you see here is the view of the setting sun from behind the rock. You can see that the alignment is near perfect, even though it wasn't planned.

The spirits of Druids walk among us at Heimhenge.