Lunar Counting from Crucuno Dolmen to its Rectangle

A fuller treatment of this article can now be found in
Sacred Geometry: Language of the Angels (2021).

Figure 1 The entrance of Crucuno’s cromlech, which opens to the south-east
[Summer Solstice, 2007]

It is not immediately obvious the Crucuno dolmen (figure 1) faces the Crucuno rectangle about 1100 feet to the east. The role of dolmen appears to be to mark the beginning of a count. At Carnac’s Alignments there are large cromlechs initiating and terminating the stone rows which, more explicitly, appear like counts. The only (surviving) intermediate stone lies 216 feet from the dolmen, within a garden and hard-up to another building, as with the dolmen (see figure 2). This length is interesting since it is twice the longest inner dimension of the Crucuno rectangle, implying that lessons learned in interpreting the rectangle might usefully apply when interpreting the distance at which this outlier was placed from the dolmen. Most obviously, the rectangle is 4 x 27 feet wide and so the outlier is 8 x 27 feet from the dolmen.

Figure 2 The in-town outlier to the east of the Crucuno dolmen.
[photo: 2007, Robin Heath]

Momentarily at least, one can consider the two lengths of (210-) 216 feet relating to 108 feet of the rectangle and I believe dolmen to centre of rectangle to be about 1105 feet. The combined monument is then as figure 3.

Figure 3 The combined monument seen within satellite data, showning two key dimensions in white, the section above magnifying the in-town components.

The Metrological Key to Crucuno

A local study group called the AAK proposed (Booklet No 20 in English) that a number of compound monuments around Carnac had a “microsite” which prefigured the larger monument, and I found this true at Lochmariaquer in the Dolmen Mane Lud (see my Sacred Number and the Lords of Time. pages 60-67.) For example, AAK thought Le Manio was a model of the Carnac Alignments. Many stone circles have “outliers” (such as Long Meg in Cumbria) and their function does seem to be to hold an alignment or a measurement or both which acts as a key to the greater monument. Such a habit would be necessary if the megalithic culture, as seems likely, had no written language: their works expressed their astronomical methods but sometimes these needed a key to the greater whole or a reference length the should be applied to the larger group of monuments.

The factorisation of numbers in the Megalithic period

The unit, 27 feet (ten Drusian steps of 2.7 feet), proves to be the key at Crucuno, for an unexpected reason; when 27 feet is seen as 29.53125 Iberian feet. That is an extremely accurate value for the lunar month, meaning that when counting in months one can use a “megalithic yard” of 2.7 feet, ten times to achieve a length that is the lunar month in Iberian feet. As a fraction 29.53125 is 945/32 visible as stone 32 representing the 32nd month in the southern kerb of Le Manio. 945 days in 32 months is accurate but Le Manio did not hint at the perfect relationship 27 feet has to 945/32 Iberian feet. The rectangle of 4 by 3 squares of side length 27 feet can be interpreted as standing for a lunar year of twelve months.

Figure 4 Further interpretation of Crucuno rectangle as the lunar year of twelve months

The power of metrology to re-factor problems

The number of days in 32 lunar months is 945, whose factors are 27 x 5 x 7, reflecting (a) the 27 foot side length and (b) the 35 in the Iberian ratio of 32/35 feet whilst (b) the Iberian numerator is the 32 lunar months. When 27 feet is divided by 32/35, the numerator is 945 and the denominator is 32 leading to 945/32 = 29.53125 feet. So 27 feet is 29.53125 Iberian feet. At Le Manio’s Quadrilateral, the 32nd stone is 945 day- inches from Le Manio’s “sun gate” (reminiscent of Crucuno’s tall stones 6 and 7).

Relation of site to the Drusian foot of 27/25 feet

In the previous article about the Crucuno rectangle, its extension downwards from being a 4 x 3 rectangle to being 4 by 22/7 (then including stones 13-17) would have allowed the Drusian foot to be enlarged by 176/175 when a square side length 22/7 x 27 feet has a perimeter of 125 astronomical megalithic yards, enabling the perfect ratio between the solar and lunar years to be manufactured from the root Drusian step of 2.7 feet. In this we are moving from purely symbolic aspects of Crucuno to its practical purpose within the astronomy practiced to achieve exact results.

The Octon Eclipse Cycle

It is likely that the dolmen marked the start of an astronomical counting using 27 foot units which are also coded for the days in a lunar month when that same length is measured in Iberian feet. The distance from the dolmen appears (on Google Earth) to be 39 lunar months since 39 x 27 is 1053 feet from within the dolmen to stone 1 of the Crucuno rectangle. This implies that the rectangle was an end-of-count artifice and, if one adds eight further units to 39 one obtains 47 lunar months which is the shortest of the reliable eclipse periods called the Octon in which 47 lunar months just exceeds 4 eclipse years or 8 eclipse semesters, hence its name Octon.

The world of eclipse cycles

The fundamental eclipse period is the Saros now used to catalogue all eclipse series, but the position of a megalithic astronomer was to approach usable eclipse periods by noting the simple co-incidence of lunar months and eclipse years [whilst the Saros (miraculously) harmonises the Draconic and Anomalistic months as well]. The traditional way of counting in early counting was via the boustrophedon, the alternate direction called after the ox-turning of ploughing fields and the Tai Plaque showed this technique in marking days millennia before Crucuno. The required eight extra lunar months therefore finds the count at the western kerb-stone numbered 20 by Thom (see figure 4). Four eclipse years complete in 46.95 lunar months, 1 day and 11 hours early or 1.46 Iberian feet – one and a third regular feet (16 inches). But the eclipse of whatever sort will require that the moon stands again on the node – that is eclipses are naturally integer relative to the lunar month. So the octon will not be a precise repeat of a very similar eclipse but it will indicate the length of the eclipse year, of which the (very accurate) Saros period of 223 lunar months has 19 eclipse years or 38 semesters (half eclipse years of 173.31 days).

Figure 5 left: Stone 10 with distinctive serpentine crack from outside the Rectangle, and stone 20 in the distance to its right, marking the 47th lunar month’s end of proposed 8 eclipse semester count. right: Stones 10, 9 and 8 seen on right when entering the south-east corner of the rectangle. The summer solstice sun rises between stones 7 and 6 to the right/south- east. [Summer Solstice, 2007]

The meaning of the outlier

It becomes clearer why there might be eight lunar months (of 27 feet) to the outlier stone, matching the 8 lunar months inside the Crucuno rectangle at the end of the count. However, singular nature of the outlier might mean it could be part of a micro-site, a summary statement in which the units of 27 feet represent eight eclipse semesters counted in the Octon cycle of 47 lunar months, and the outlier stone would then symbolise the lunar eclipse which occurs at stone 20 in the actual count.

The implied counting process

 Whenever an eclipse occurs, a new count is started at the dolmen and hence the distance between the dolmen would have a number of counters, possibly stones placed at the end of each 27 foot length of the count to the rectangle. The outlier perhaps expressed this principle of “marking” the progression of eclipse counts. Every full moon (of a possible lunar eclipse) causes the marker to move and when a count enters the Rectangle’s final end it might be that day counting started using Iberian feet. Eclipses would return to the dolmen and after a few such counts they would change as eclipses until they no longer marked an eclipse. A schematic of the whole monument is then as figure 5. There is a slow drop of 4- 5 metres to the rectangle over the 321 metres from the Dolmen.

Figure 5 The Crucuno Monuments as a Single Whole


In continuity with the Le Manio Quadrilateral’s 32nd stone being 945 day-inches from the “sun gate” of Le Manio, the 27 foot unit implied within the Rectangle is also, by reason of the above factorization, equal to 29.53125 Iberian feet, that is, to the lunar month in days. This insight then appears to calibrate 39 units of 27 feet from the Dolmen to the Rectangle, the twelve squares of the 4×3 Rectangle providing an “area of attention” at the end of a count lasting just eight more lunar months. In 47 lunar months, eight eclipse semesters end just (1 day and 11 hours) before 47 lunar months. There would be more than one ongoing eclipse count since each lunar eclipse belongs to the Octon cycles recurrence of eclipses. As each lunar eclipse count nears an end, having entered the Rectangle, days rather than months can be counted as Iberian feet of 32/35 feet, especially in the 47th month. The end of the 47 lunar month count is stone 20 of the Rectangle.

The whole count is summarised in 8 units of 27 feet to the Outlier, then signifying the aim of counting 8 eclipse semesters over just less than 47 lunar months. The Outlier appears displaced from the counted alignment by 18.6 Iberian feet (17 feet), the excess length of the solar year (365.24 days) over the eclipse year (346.62 days) of two eclipse semesters, making the Outlier part of a “microsite” which speaks of the compound monument of Dolmen and Rectangle.

Getting to know the rectangle’s stone numbers

I have prepared a video to introduce the rectangle’s stone numbers:

Getting to know the stones – A video with no sound – [Summer Solstice, 2007]

Acknowledgement: Thanks to Howard Crowhurst and the local ACEM group ( for inviting Robin and I to their week-long Solstice 2007 event, which began at Crucuno Rectangle. It has taken me over ten years to think what it might have meant.