In previous artices in this series it has been shown how disingenuous criticism of Alexander Thom's flattened circle geometries were, and how this has prevented further progress in understanding how they could have been (a) constructed, without ropes by using a grid, and (b) how the type-A for example can be organised using the multiple square geometries of megalithic Brittany (4700-3000BC). The location of useful astronomical geometries within a flattened circle, once drawn using squares rather than ropes, implies that flattened circles could have been a standard useful design for calculating and tracking important time periods. This idea can be taken further into the domain of observational astronomy, if such circles allowed observers to know which parts of the ecliptic are rising and setting on the horizon. In this regard, the circumpolar stars offer a natural timepiece rotating in the north, of a clear pattern of distinct stars and constellations: a design which is also circular.
In Sacred Number and the Lords of Time, I propose that circumpolar astronomy was practiced in the megalithic, from Brittany onwards, and this can account for the northerly alignments found within monuments, as being used to track sidereal time through either (a) direct viewing of the circumpolar region or (b) by noting the azimuth on the northern horizon of key (marker) stars which never set. The naked eye astronomer can then watch the circumpolar region and know the sidereal time through a direct experience even though there are distortions due to the angle of the ecliptic relative to the celestial equator, the ecliptic being skew to the polar axis and the circumpolar region being somewhat distorted by the act of reducing stars to their azimuth on the horizon.
With this in mind, another megalithic use for the Type A flattened circle can be imagined once one observes when the winter solstice point (on the eclipic) rises on the eastern horizon and when the summer solstice points rises, the time between is eight hours (in southern Brittany, 4300 BC). It then takes sixteen hours for the winter solstice point to again rise on the easter horizon. This observation can be done on winter solstice sunrise so that the sun will be setting eight hours later. Observations after summer solstice sunrise will offer a time (at Carnac) of sixteen hours. The generalisation that the length of the shortest winter day or longest summer day at a given latitude could tell the megalithic astronomer how to calibrate the circumpolar disc. In north-west Europe though, the days division of light and dark at the extremes of the year was very simple and the megalithic observer found the duration of the dark period (night) for one solstice equals the duration of the light period (day) for the opposite solstice. At latitudes near southern Brittany one also finds that the lesser period is 8 hours long and the longer period 16 hours as below.
The sun rises with the extreme northerly tip of the ecliptic at summer solstice and takes 16 hours before setting, at which point the most southerly tip of the ecliptic is rising on the horizon, and a night of 8 hours begins before the sun again appears still sitting near the northern extreme of the ecliptic. The Autumn equinoctal point, where the ecliptic drops below the celestial equator, rises at the midpoint between the solstitial points, and eight hours of earth rotation from each. The Spring equinoctal point sits similarly between the solstitial points, and four hours after the winter solstice point and four hours before the summer solstice point. This time sequence is forever slowly changing due to the progress of the sun along the equinox in (above) an anti-clockwise cycle through the year, with about 365 steps between positions at sunrise. This manes that any counting regime, of days around a circle representing a solar year, is naturally congruent to such a circumpolar understanding.
One can look at the circumpolar sky using software to see the actual pattern of stars that would have greeted the astronomers 6000 years ago, Firstly, one can see the circumpolar stars at summer solstice sunrise (or by symmetry, at winter solstice sunset):
image made using CyberSky
One is struck by the obvious fact that the Big Dipper is behaving like an hour hand for what we call the "two o'clock" angle of a modern clock's hour hand. In fact, the big dipper appears carved as a pattern of dots in the door jamb of La Table des Marchants, with an implied geometry of the 3-4-5 triangle, whose smaller angle defined the azimuth of solstices relative to east-west (sunrise or sunset).
If the midsummer sunset is observed in the northern sky at this epoch one sees the distinctive "question mark" down at the six o'clock position:
image made using CyberSky
The megalithic observer would therefore conceptualis the rotating pattern of stars according to the picture below, shown in the six o'clock position.
By looking at this timepiece, the parts of the ecliptic that were rising or setting on the horizon could be known, with particular focus on the four "gates" of the solar year, the solsticial and equinoctal points, in a pattern deduced from noting the dark periods of the two solstice days as in the ratio one third (summer) and two thirds (winter) of a complete (sidereal) day of one earth rotation. This same circle is the year circle of 365 days, reducing astronomy to a design naturally visible at the circumpolar region and which is elegantly presented in the Type-A flattened circle, a circle based upon the division into one third and two thirds.