At megalithic sites, the only alignment of note on the northern horizon has usually been the direction of the north pole or "true" North on the site plan. "Megalithic" cultures worldwide, both the later manifestations in the Americas or the old world cultures of Northwest Europe or Egypt, built structures oriented in a very accurate way to North. The builders of the Great Pyramid for example or of the geo-glyphs of the Amazon rainforest, seemed to have had an unexpectedly good method for determining North, no easy task when a pole star is never exactly north.

Using a north pole star is not accurate enough without modern equipment so that in practice naked eye astronomers were better measuring the extreme elongations, in azimuth, to east and west of suitably bright stars. The two most obvious stars to choose, amongst the circumpolar stars, are the magnitude 2 stars of the Great Bear and Little Bear constellations, now called Dubhe and Kochab. Other stars in these constellations were also relevant in 4000 BCE, such as our present pole star Polaris (tail star of Ursa Minor) and the tail star of Ursa Major, Alkaid (Arabic: "the head of the mourners", the big dipper then being seen as a Bier). The diagram below shows how each circumpolar star describes a circle every time the Earth rotates, and that to East and West, each star will achieve a maximum elongation that will stand above the horizon and can be measured in azimuth - the angle relative to north on the horizon.

Figure 1 Time exposures facing North reveal a whirlpool of circumpolar stars where even feint stars look bright. All circumpolar stars describe a circle around the north pole every time the Earth rotates. As a consequence, on the horizon the star will appear at a maximum angular distance from true North that will be the same east or west. This enabled the megalithic builders to define an accurate bearing to the north pole for their structures. Even when there is a north pole star, it will not lie directly north at all times, so this method was required.

At Le Menec, there is good evidence that the primary marker star was Dubhe, alpha Ursa Major (see The Meaning of Le Menec). Having established this method as possible and likely for megalithic circumpolar astronomers, the horizon to the north becomes far more meaningful as regards alignments that previously could only be noted or explained based upon symbolic or geometrical interpretation. One such feature is the 18 degree alignment to north found to emanate from the base of the Grand Menhir or Er Grah, to the east of Le Menec. The "Tumulus of Er Grah" looks like a shadow for the menhir, a low level and extensive structure made of rocks and orientated relative to the north, as in this charming diagram below that is looking north.

Figure 2 Looking North: Er Grah was the largest standing stone ever raised and it was very heavy but it appears to have fallen due to earth tremors. The tumulus aligned at about 18 degrees west of north is shown to the left (west) and the Table des Marchands to the east. [This picture is from Association Archeologique Kergal, Etudes et Travaux, No 6, page 15]

An archived Google Earth shows the site from above, as follows:

Figure 3 An Ariel View of the Er Grah site gives a likely angle for its tumulus of about 18 degrees west of north.This can be seen as a possible orintation of a bright circumpolar star in its maximum western elongation.

One must remember that in the ancient past, societies seem often to have created a spiritual centre upon the Earth by placing a singular standing stone which was then given polar associations, the pole indeed getting its name by being an invisible pole to the north that defines the axis of the (turning of the) World. In this case, the tumulus invites a search for a suitable star around 4000 BCE, that whould have had a maximum angle to north of around 18 degrees west. CyberSky 5 enables such a search to be relatively easy to reveal the star Alkaid, eta Ursa Major, as having a maximum elongation (to east or west) of just over 17.5 degrees between 4000 and 3900 BCE, see below.

Figure 4 The circumpolar region around 4000 BCE, as shown using CyberSky 5 software. The vertical lines in yellow show constant horizon azimuths, allowing Alkaid, a magnitude 2 star, to reach about 17.5 degrees west of north, an angle quite probably referenced by the tumulus of Er Grah.

It therefore appears that the constellation Ursa Major had the two stars at its ends, both magnitude 2, used as significant markers for accurately determining north and also available for tracking the rotation of the earth, Dubhe at Le Menec's western cromlech as described in The Meaning of Le Menec and Alcaid at Er Grah in Locmariaquer. The literary association of bears with the pole extends into the polar myth of King Arthur, whose name derives from that for bears and the arctic, as expressed in a drawing by Hachette:

Figure 5 A Bear on a pole held up by the Chinese acrobat but reminiscent of the polar god Druva, who stands on one leg and holds up the sky on a nail.

Below I repeat figure 6 of The Meaning of Le Menec in which the initial stones have alignments to the eastern maximum elongations of circumpolar stars in 4000 BCE. Row 6 from the north starts with a stone that was aligned with Dubhe, then deliberately aligned to the cromlech's easternmost point since the forming circle of the cromlech's egg shape could then represent the circular path of Dubhe during the rotation of the Earth.

Figure 6 Some of the associations between circumpolar stars and stones in the western alignments. These alignments are all to the maximum easterly elongations, perhaps established during the building of the sidereal observatory and only later formalized into leading stones at the start of different rows. Dubhe was then selected as the primary marker star for the Le Menec observatory.

The angles generated by circumpolar astronomy for specific stars will increase in horizon azimuth angle as latitude upon the earth, for sites, increases. Long Meg in Cumbria, Northern England, is a stone ring at latitude 54 degrees and 44 minutes. Long Meg's ring is a north-facing Type B flattened circle that appears also to point to Alkaid but at a maximum elongation to east and west of north equal to 20.5 degrees because of the higher latitude of the site. However, the characteristic V-shape of alignments is quite similar to that for Er Grah, as can be seen in Figure 7.

Figure 7 Long Meg and her daughters appears suited and probably was designed to use the star Alkaid in a similar way as described in The Meaning of Le Menec. The irregularities of horizon altitude leave this type of circumpolar astronomy unaffected. All of the arcs in the geometry are based around the double square crucial to this technique and the length of 1394 inches as side length is enabling of a circumference having 365 parts, naturally suitable for dividing up the rotation of the Earth to establish sidereal time.

The menhir Er Grah would be at the bottom of the V-shape and the west of north angle of its tumulus is symmetrical with a feature made by archaeologists who were looking for the ancient remains of holes large enough to accomodate the fallen Grand Menhir. No hole big enough was found but rather a sequence of holes used for smaller standing stones. Exact bearings are not known and it is therefore clear wherefrom the alignments should be measured. However, when Le Menec's western cromlech is considered, there is no need for a menhir at the backsight from which observations are made and a good amount of ancient work would only have been possible if done using wood and rope.

Figure 8 presents the case for both the maximum eastern and western elongations of Alkaid to be represented as the alignment of the Tumulus of Er Grah and the line of stone holes now covered with similar rocks aligned to the east. An observation point near but south of Er Grah would enable a circle of the same diameter as Le Menec's western cromlech (in white) of 1394 inches, with circumference 365 units of two feet (24 inches). (1394 inches being 17 megalithic "rods" of 82 inches).

A follow up article will look more deeply into the possible circumpolar astronomical alignments of Locmariaquer's Er Grah complex and their relation to events to the east and west.