Friday, 30 July 2010

The silver apples of the moon, golden apples of the sun...

I'm not one for imagining complicated astronomical alignments built in to Neolithic/ Bronze age structures. I approach the idea of sun+moon alignments within massive wood or stone structures from the point of view of someone who has made labyrinths, and knows first hand that large structures are difficult to make accurately and that accuracy is rarely the point...

There is just something magnificent about creating something so large and complex out of earth and stone, it instantly becomes weird or numinous or perhaps more correctly, sacred space.

Aubrey Burl had caused me to believe that the midwinter moon always rose in the North East; and that the Cotswold Sevens -long barrows- are aligned NE/SW so that the midwinter moon would illuminate the bones, deep within the gloom. It is also true that Stonehenge and Woodhenge are both aligned that way...but the midsummer sunrise is on the same azimuth as the midwinter who is right, the Druids or Aubrey?

Now there's a thing, azimuth. It means -and I didn't know this until yesterday- the compass alignment expressed in degrees: so North is 0, East is 90, South is 180 and West is 270. Latitude and longitude do have an effect on where the sun and moon are seen to rise, but give or take a few thousand years, plus the fact that the moon has a eighteen point something it is only in the same place in the sky once every eighteen point something years, all in all I think using azimuth values for London are accurate enough for my purpose.

And there is the moon standstill cycle, meaning that there is a minimum and maximum range of azimuth values:
A major (or minor) lunar standstill always happens near an equinox; and what's more, it happens when the Moon is at or near quarter phase. A major lunar standstill faithfully occurs within one week of a lunar or solar eclipse, and oftentimes takes place right between a lunar and solar eclipse. For instance, this year's March 22 southern major lunar standstill comes one week after the March 14 lunar eclipse and one week before the March 29 solar eclipse; similarly, the September 15 northern major lunar standstill is flanked by the September 7 lunar eclipse and the September 22 solar eclipse.
To be honest I was put off, the moon seemed very difficult!

The moon and sun calculator are here [LINK].

So, using 2006 (after checking out other years and drawing lots of diagrams!) because that year had the maximum range of values, the midsummer sun does indeed rise in the North East (which is an azimuth of 45) and it doesn't really matter if its a special moon-stand-still year of not. The midsummer sun rises at 49 degrees and sets at 311.

Meanwhile the equinox sunrise, both autumn and spring, is at 89 degrees (East is 90 degrees) and sun set is at 271 (West is 270).

It is the moon though, more than the sun, that proves fascinating.

The moon always rises on the Eastern side of Woodhenge. It sets in the West and North West, but never enters the North to rise or set. The midwinter full moon gets the closest to the North of all the moons.

I seem to recall something about the North being the 'Land of the Dead' because neither the sun or moon ever go there.

In December and January the midwinter full moons cast a path of silver for the midsummer sun. The midwinter moon is a North-East moon rising from the brimming lip of the world somewhere between 40 degrees to 50 azimuth (the same path the sun takes when it rises at midsummer).

The January, February and March full moons rise towards the East and cross the Northern sky to set increasingly in the North West. The New moons go the other way, rising at first in the South East and progressing with each new moon rise, towards the East, and set in the South West.

The March full moon and new moon rise in the East -between an azimuth of 83 and 86 degrees- with only a few degrees of difference between them. If you want to know when it is March, wait for the full and new moons to rise from the same place...

In April, May and June the moons have swapped places with the new moons now rising in the North-East and setting in the North-West and the full moons rising in the South East and setting in the South West.

In July, August and September the new moons still rise in the North East but are now moving towards the East and setting in the North West. The September full moon does an odd thing, it crosses the path of the sun into the West; I mean it crosses the 270 degree line just a fraction. This is the only time in the year when the moon does this. The full moons are moving from South East towards true East, with the most easterly full moon almost at true East.

For October, November and December the full moon is back in the North East and heading North to hang like the Queen of Ghosts at the entrance to Stonehenge, and the new moons are turning away from the East, heading West.

Yes, I drew lots of diagrams and satisfied myself that the difference in where the moon rises and which direction it moves in, is significant enough for even a dolt like me to be able to work something out about what time of year it is.

I particularly liked the September full moon crossing the sun-path.