Everyone knows about the primary Stonehenge solstice axis - it runs from Summer Solstice Sunrise to Winter Solstice Sunset.
Every June 21st (or thereabouts - it varies depending on leap years and other things), thousands of people turn up and spend the night in and around the monument waiting for the Sun to rise out of the Heelstone.
And every December 21st (or thereabouts), hardly anyone bothers to show up specifically to stand by the Heelstone to watch the Sun set into the centre of the monument just to the left of Stone 56 in what would have been the gap between the two uprights of the tallest trilithon had it not collapsed in antiquity.
But there's a second solstice axis, which runs from Winter Solstice Sunrise to Summer Solstice Sunset.
I first became aware of this as a result of reading Prof. Gordon Freeman's book "Canada's Stonehenge" back in 2009. In it, Gordon discusses the alignments of a First Nation's medicine wheel in Alberta and also those of Stonehenge. Gordon came to the UK to carry out observations over a number of years from the 1990s onwards, making him somewhat unusual in archaeoastronomy terms in that he actually used his own eyes on site to arrive at his conclusions instead of relying only on plans, maps and computer simulations.
In the book (2nd edition is called "Hidden Stonehenge") he pointed out that there's a direct sightline that runs through the monument on a roughly NW-SE axis which points directly at the rising point of the Sun over Coneybury Hill at Winter Solstice, and at the setting point of the Sun into Fargo Wood at Summer Solstice in the opposite direction.
Gordon had never been lucky enough to make a direct observation of the Winter Solstice Sunrise on the actual solstice due to adverse weather every time he'd visited. To combat this, he'd projected the Sun's solstice rising position based on photos he'd taken of near-Solstice risings that he had been able to observe.
Intrigued by this, I resolved to try and make some observations of my own.
The alignment towards Winter Solstice Sunrise that Gordon suggested runs on the dotted line shown in the following oblique aerial view...
... starting from the visitor path NW of the monument, it goes via the midpoint between Stones 22 and 21 of the outer circle, then through a notch about 1.5m above the ground in the SW edge of Stone 58 of the western trilithon, skirts the NE edge of Bluestone 69 then the NE edge of Stone 53 of the SE trilithon and passes over the (now-fallen) stump of Stone 8. When S8 was originally standing, the line would have skirted its SW edge.
The view along this sightline from the visitor path is like this, with the relevant stones numbered and the notch indicated:
The closeup view (to show the Coneybury Hill horizon) is like this:
Note the very handily placed electricity pylon on the horizon for reference.
In 2011, a couple of weeks before Winter Solstice, I was able to get some photos of the rising Sun over Coneybury Hill standing on the alignment on the SE side of Stonehenge (to get an unobstructed view), which I montaged together with a wider view taken through the notch - both sets using the pylon as the reference mark.
Knowing the declination of the Sun on the 10th December, the apparent width of the solar disc and the declination the Sun would have had in 2500BC I was able to create the next image to indicate the rising position of the Sun on Winter Solstice in our era and also what it would have been when Stonehenge was built.
As luck would have it, on the 22nd December 2011 there was a hazy sunrise that allowed me to have some confidence my projection so far was about right.
Knowing the exact azimuth of the Sun at the instant the photo was taken, and being able to calculate the azimuth that the rising Winter Solstice Sun would have had in 2500BC (when the angle of the Earth's axial tilt was 24° rather than 23.5°) I was now able to construct the equivalent view back when Stonehenge was built...
...and this (via the handy electricity pylon) then allowed me to create an updated montage of the view seen along the alignment via the notch itself, both now and in 2500BC.The alignment first identified by Prof. Gordon Freeman is targeted like a rifle sight at the precise position of Full Orb of the Winter Solstice Sunrise over Coneybury Hill when Stonehenge was built.
I'd been corresponding with Gordon since I'd first read his book, and sent him my results.
But.
There's another wrinkle.
Hidden from view in that oblique aerial photo which shows the path of the alignment through the monument is another stone. A very important stone. A unique stone. In a very specific position.
It's this one.