We know already that some alignments are astronomically aligned - toward the rising and setting points of the sun at the solstices or other times of the year, or toward the rising or setting points of the moon at lunar maxima or minima. However, these have not been systematically studied - this is part of the next phase of research in the Ancient Penwith project.
There are two distinct issues here. One is the rising or setting points of sun and moon on the local horizon, as seen from any ancient site - and that horizon might be higher or lower in elevation (height) from the place of observation, called the backsight. This means that 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 is a level-horizon azimuth, which holds true whatever elevation the local horizon is. Unless one is looking over the sea or across a relatively flat landscape, this is a theoretical more than an observational azimuth.
So the two big variables here are the azimuth
and the elevation
. The azimuth is the number of degrees from true north, measured eastwards from north or rightwards along the horizon. So east is 90°, south is 180° and southwest is 225° (180+45°).
The elevation is the vertical height of any point on the horizon (the foresight) relative to the place of observation (the backsight). Usually this is just one or two degrees up or down, but it makes a difference - as is demonstrated in the diagram on the left (drawn by Prof Alexander Thom), showing the influence of the horizon on the rising point of the sun at solstice, at the latitude of 50° north, the latitude of West Penwith.
The ancients of Penwith and the European megalithic culture were obsessed with time - rather like the Mayans, later on. Not just with counting time, as we do when we say "15th June 1904", but with understanding the nature and the passage of time - in the sense of "the times are changing".
They sought to play an active role in the movement of time and season, seeing their fortunes to be closely connected with this relationship with time. The relationship between the heavens, humanity and the earth needed to be in order, and if this was so, all would be well. They sought to build time and its cycles into the location and design of the ancient sites they built.
Time was fixed by creating astronomical alignments and orientations, and also by the number of stones in and the mathematics of stone circles. This would in effect dedicate a site to marking one or a few specific times of year or of the nineteen-year lunar eclipse cycle. A key period was the Metonic cycle, named after a Greek philosopher, Meton, who was alleged to have discovered it - though this was 2,000 years later than the stone circle building period.
The Metonic cycle brings together the solar and lunar calendars, being made up of 6,939.6 days, which is equivalent to 19 solar years, 20 eclipse years, 235 synodic months (cycles of lunar phases), 254 sidereal months (lunar orbits of the heavens), and 255 draconic months (conjunctions with the North Node or Dragon's Head - an eclipse-related cycle).
In our study of ancient Penwith it is necessary to find out which sites and alignments have astronomical orientations, and which do not. As a start, the azimuth orientations of all alignments in Penwith have been calculated, and this is presented below.
However, calculating alignment azimuths does not mean we suggest many of the alignments are astronomical - it is simply a means of finding out. More work needs doing on this.
The problem with studying alignment azimuths is that it presumes a flat landscape and horizon, which, in many cases, is not the case. It is possible that the ancients might have worked with theoretical level-horizon azimuths, though it is more likely that they were more interested in local azimuths as seen observationally from certain specific sites - the visible horizon.
However, you will notice that there are concentrations around certain azimuth degrees. This is either a matter of chance, or not. Until we have carried out our archaeoastronomical field survey, we cannot tell. The figures are presented below, for your interest. You can also download a PDF file here.