Independent researcher Simon Banton has published a clear and accessible blog post explaining how he used the Moon as a proxy for the ancient Sun to test and visualise Stonehenge’s secondary solstice axis.
Photo of the lunar proxy of the Midwinter Solstitial Sunrise over the Altar Stone - photo - Simon Banton
The Problem
The Earth’s axial tilt (obliquity) was slightly greater (~24°) when Stonehenge’s sarsens were erected around 2500 BC. This means the Sun no longer rises and sets at exactly the same horizon positions the Neolithic builders saw. Direct observation of the ancient winter solstice sunrise is impossible today.
The Clever Lunar Solution
During a major lunar standstill (which we’re in now), the Moon reaches more extreme positions on the horizon than the modern Sun. Banton timed his observations for July 2024/2025 so the Moon rose very close to where the winter solstice Sun would have appeared 4,500 years ago.
He captured the event from a position aligned with the proposed sightline — looking through the notch in Stone 58 and the edge of Stone 53 toward Coneybury Hill. The results are striking: the Moon acted as an excellent stand-in, confirming the alignment works.
Why This Matters
- The sightline is tightly framed and runs parallel to and directly above the long axis of the Altar Stone.
- It forms an ~80° angle with the primary solstice axis (summer sunrise to winter sunset) — exactly as expected for the solstice extremes at Stonehenge’s latitude in 2500 BC.
- This supports the earlier proposal by Gordon & Phyllis Freeman and reinforces the idea that the monument was deliberately designed around two intersecting solstice axes from the start.
You can read Simon’s blog post here: Using the Moon as a Proxy for the Ancient Sun
(Note: Simon has also written a more detailed peer-reviewed version which is currently behind a paywall, https://doi.org/10.1558/jsa.33686 )
The Coneybury Hill sightline is the part I would most like to test properly, because it is close enough for the horizon model to matter.
ReplyDeleteI have built a real-time model of the monument that computes the sky from published ephemerides (Meeus, VSOP87D, Laskar's obliquity solved per epoch) over NASA/USGS SRTM radar topography of the plain, so I can run the Stone 58 notch to Stone 53 edge line against a real skyline rather than a flat horizon. Happy to do that and publish whatever comes out, including if it does not support the 80 degrees.
One caveat I would rather raise myself. SRTM is a radar surface model, so it includes present-day canopy. On a distant horizon that is negligible in altitude terms. Coneybury is close enough that a few metres of tree height could move the horizon altitude, and therefore the azimuth, by more than the effect being measured. So I would want to re-run it on Environment Agency LIDAR bare-earth and report both numbers rather than one.
For calibration on my own figures: from a survey-derived primary axis of 49.9 degrees I get the 2500 BC midsummer sunrise over the SRTM skyline at 49.08, and the midwinter sunset about two tenths off. That would make midwinter the tighter fit, but I do not trust the comparison yet, because I do not know the uncertainty on the axis definition itself. If the spread across reasonable definitions exceeds the 0.6 degree gap between my two results then it is not a result at all.
Which definition of the primary axis do you work from?
Hi Simon is the man to ask, this is his method and discovery - link to his blog in th epost.
DeleteSimon writes:
ReplyDelete"4,500 years ago, when Stonehenge was built, the angle of tilt was roughly 24° give or take a couple of minutes of arc."
Imagine the avenue, heelstone, altar, great trilithon, etc. alignment(s) is actually the maximum of 24.5°! Whoa
8700 BCE is what I have found to be the moment however.
I'd like to see photographic, etc. representations of the sun at it's minimum of 22.1°, as I will probably not be able to visit the site in 11,800 CE.
Will the sun still be visible in the "notch"?