Archaeoastronomy | Azimuths
Archaeoastronomy | Azimuths
While progress is locally being made in archaeoastronomy, research has not yet been sufficiently systematic to identify how many astronomical alignments there are in West Penwith, and the patterns of their application at ancient sites.
Lower down: Calendrics - Alignment Orientations - Alignment Azimuth List
Two distinct issues are involved. One is the rising or setting points of sun and moon on the local horizon, as seen from an ancient site. That horizon might be higher or lower in elevation (height) when observed from the place of observation. At that place, the sun or moon will rise at a different degree or azimuth from the place where it would rise if the horizon were level.
The other issue concerns a level-horizon azimuth, which holds true whatever elevation the local horizon is, as if the horizon were level and flat. Unless one is looking over the sea or a flat landscape, the level-horizon azimuth is a theoretical more than an observational azimuth.
In Professor Thom's diagram below, the double circle is the sun rising over the sea - a level horizon (if you're standing at sea level, not on top of high cliffs). The lines above the sea horizon represent horizons of different heights, up to two degrees higher in elevation, as seen from where you're standing. As you can see, the place where the sun would rise would move further to the right, or southwards, the higher that the horizon is. That left-right motion is the azimuth. The opposite is the case with the setting sun (it goes right-up to left-down).
The two big variables are the azimuth and elevation. The azimuth is the number of degrees from true north, measured eastwards or rightwards from north along the horizon. So:
Northeast is 45°,
East is 90°,
Southeast is 135°,
South is 180°.
Southwest is 225°,
West is 270° and
Northwest is 315°.
North is at 360°, usually called 0° and the degree immediately to the left of it is 359°.
The elevation is the vertical height of any point on the horizon (the foresight) relative to the place of observation, where you're standing (the backsight). Usually this is just one or two degrees up or down, but it makes a difference. In some cases, at sites in valleys (such as Mên an Tol), the horizon can be high (at Mên an Tol, looking eastwards, it is 15ish° or more).
If you were building a chambered cairn or a stone circle and you wished to make an orientation to the summer solstice sunrise at that place, you would observe it at the site, but you could also calculate it mathematically if you knew the elevation and the level-horizon azimuth of sunrise at summer solstice. In Penwith on a level horizon it is 50° east or rightwards of north. If you're looking uphill, it will be less, and downhill it will be more than 50°.
Calendrics
Near-total solar eclipse, 20th March 2015, at Botrea Barrows
The ancients of the megalithic period were obsessed with time, preoccupied not just with counting time but with understanding and interpreting the nature and the passage of time, and to plan activities accordingly. They were both astronomers and astrologers.They sought to play an active role in the movement of time and season. They felt their fortunes were closely connected with the fluctuations of time and their relationship with it.
They wanted to do their best with the available qualities of time, and to foresee coming times. The relationship between the heavens, humanity and earth needed to be in harmony. They built time cycles into the location and design of their ancient sites. They fixed time into the dimension of space, into the landscape.
Time was fixed into space by creating astronomical alignments and orientations to the rising and setting points of sun, moon and stars. It was also fixed through the number, mathematics and arrangement of stones in stone circles. This would dedicate a site to marking a few specific times of year or of the lunar eclipse cycle.
The ancients had two calendars - one solar and one lunar. The solar calendar divided the year into eight segments, anchored in the solstices and equinoxes. The lunar calendar was measured from newmoon to newmoon (29 days and 12 hours long).
A key period was the Metonic cycle. The Metonic cycle brings together the solar and lunar calendars, which coincide once every 19 years - specifically 6,939 days. Here various sun-moon cycles coincide.
It is equivalent to 19 solar years, 20 eclipse years (cycles of eclipses), 235 synodic lunar months (cycles of lunar phases), 254 sidereal lunar months (lunar orbits of the heavens), and 255 draconic months (conjunctions of the Sun with the North Node or Dragon's Head - an eclipse-related cycle).
Alignment Orientations
In Penwith it is necessary to do a comprehensive study of all sites and alignments to identify astronomical orientations. Thus far, it has been patchy, focusing on certain sites (it's early days in this research). Not all sites have astronomical factors involved.
The azimuth orientations of alignments between sites in Penwith have been calculated (as if on a flat landscape), and this is presented below in a downloadable PDF. Further research will continue: this has been pursued particularly by archaeoastronomer Caroline Kennett - see Archaeoastronomy Cornwall.
Known astronomical orientations (there are probably many more) are shown on the Penwith alignments map in blue. Here's a selection:
A01. Mulfra Quoit - St Michael's Mount. Winter solstice sunrise as seen from Mulfra Quoit in 3500 BCE at the time of its building. Azimuth: 128.5˚.
A02. Trencrom Hill - Tregonning Hill. Midwinter solstice sunrise. Azimuth: 124.4°.
A04. Chun Quoit - Carn Kenidjack. Winter solstice sunset as seen from Chûn Quoit looking toward Carn Kenidjack. Azimuth: 232.57°.
A06. Zennor Quoit - Sperris Quoit. Lunar major standstill rising point as seen from Zennor Quoit, looking toward Sperris Quoit. Azimuth: 38.4°.
A07. Carfury - Cudden Point. Beltane-Lammas sunrise alignment as seen from Carfury menhir. St Michael's Mount and Cudden Point align with each other. Azimuth: 117.0°.
A08LP. Castallack B - Swingate B. Winter solstice sunrise. Azimuth: 127.6°.
A09LP. Castallack menhir - Swingate A. Winter solstice sunrise. Azimuth: 128.5°.
A10. Pordenack Point - Caer Brân - Castle an Dinas. Summer solstice sunrise and winter solstice sunset alignment, aligning three of Penwith's four Bronze Age circular enclosures. Azimuth: 49.62°.
A11. Pordenack Point - Bartinney Castle. Astronomical alignment to the lunar maximum north rising point (40.62°). Azimuth: 40.7°.
A13. Castle an Dinas - Conquer Cairn. Beltane-Lammas sunset alignment from Castle an Dinas to Conquer Cairn. Azimuth: 294.2°.
A14. Castle an Dinas - Trencrom Hill. Beltane-Lammas sunrise line as seen from Castle an Dinas, with the sun rising over Trencrom Hill. Azimuth: 67.5°.
Critical rising and setting points of the Sun and Moon at the latitude of West Penwith | ||
Azimuths West Penwith 2500 BCE | Rising | Setting |
Sun Winter Solstice | 127.9° | 232.1° |
Sun Candlemas/Samhain | 109.8° | 250.2° |
Sun Equinox | 89.0° | 271.0° |
Sun Beltane/Lammas | 64.4° | 295.6° |
Sun Summer Solstice | 49.5° | 310.5° |
Lunar Maximum North | 39.3° | 320.7° |
Lunar Maximum South | 137.6° | 222.4° |
Lunar Minimum North | 58.6° | 301.4° |
Lunar Minimum South | 119.1° | 240.9° |
Azimuths are measured clockwise from North. North=0°, East=90°, South=180°, West=270°. Some azimuth inaccuracies (acceptable within 1°) are explained by differences in the elevation (height) of one site as seen from another | ||
Various sites emerge with a number of astronomical alignments, including Castle an Dinas, St Michael's Mount, Tregeseal, Trencrom Hill, and other likely candidates are Carn Galva, Carn Kenidjack and Boscawen-ûn.
The objective in making astronomical alignments was to plug time into space, and particularly into certain sites. This would empower those sites at the time of year marked out in the landscape through an astronomical orientation. Different sites would therefore be utilised at different times of year.
As circular ceremonial sites, it is likely that Caer Brân, in the centre of the peninsula, was used at summer and possibly winter solstice while Castle an Dinas was used at Beltane and Lammas - by dint of astronomical alignments at those sites.
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