Major Lunar Standstill, Silbury Hill

Major Lunar Standstill over Silbury Hill in Wiltshire.

Every 18.6 years the Moon reaches maximum declination relative to the Earth's equator. Whilst the Sun can reach a maximum of 23.5 degrees North or South of the equator (at the annual solstices), at a Major Lunar Standstill (also known as a Lunistice) the Moon can reach 28.7 degrees North or South of the equator. (In effect, the 5.1 degree inclination of the Moon's orbit gets added to the 23.5 degree tilt of Earth's orbit relative to its equator.) This is particularly noticeable around summer Full Moons near the lunistice, when the Moon hangs noticeably low in the sky all night. Last night the maximum elevation of the Moon above the horizon at Silbury Hill (latitude 51.4 degrees North) was just 9.6 degrees, which is close to the lowest possible in the 18.6 year cycle.

Many archaeologists believe that Lunar Standstills were significant to Neolithic communities, including those who built Silbury Hill, 4,500 years ago. There is evidence that elements of contemporaneous monuments such as Stonehenge and Calanais were aligned to the extreme rising or setting points of the Moon in this cycle.

To capture the Major Lunar Standstill I set up a fixed camera with a wide-angle lens north of Silbury Hill and made a set of bracketed exposures every four minutes from moonrise at 2035 to moonset at 0311. I then stacked them using Lighten mode to show the trajectory of the Moon on a single composition. Fortunately the sky was pretty much clear all night, with only a few frames lost to cloud towards the end of the sequence.