A connection to both lunar and solar observations has been recognised in the design of several prominent stone-circles such as Callanish, Stonehenge, Almendres, Newgrange and the numerous RSC's (recumbent stone circles) of Scotland, which are identified with lunar observation.

The connection between stone circles and astronomy is not however, so clean-cut. A visit to almost any circle is all one needs to realise that although certain stones were selected to demonstrate a preference for orientation (with portal stones or through a gradation in height), the stones of most circles were placed evenly apart around the circumference, having a symbolic placement rather than a functional one. The choice of stone over wood added to the selection and transport of specific types of stones over long distances also demonstrates the importance of stone itself to the circle builders.

 

The Nabta stone-circle is the only megalithic construction of its kind in all Egypt. It is positioned exactly on the Tropic of Cancer.

The people at Nabta built an observatory — a 12-foot (4-meter) circle of huge slabs of stone, with four pairs of taller stones aligned opposite each other. Two pair provided a "window" on the solstice sunrise, while the other two aligned on an almost-perfect north-south axis. Nabta's calendar circle was used at least 6,000 years ago, and probably earlier

Nabtans erected several other megaliths in the area - dark stones up to 3m above the desert landscape, scattered across a square mile. Some of the megaliths formed north-south and east-west sightlines, like a giant stone compass, and probably remained visible when the summer inundation filled the Nabta basin.

"We see two kinds of astronomy here — solstice alignments and cardinal alignments," says J. McKim Malville, a professor of astronomy at the University of Colorado at Boulder and a member of the team that confirmed the alignments in a paper published earlier this year.

"The astronomical nature of the site was clear while we were there," says Malville. "These alignments are so simple and straightforward, there's no doubt about them."

(More about Nabta)

Scotland is home to hundreds of 'Recumbent' stone circles. These circles are usually fairly small, the largest being (Innesmill (B5/1 at 110 ft diameter). Recumbent circles in the Grampians of Scotland have been shown to have a primary association with the observation of the extreme setting points on the lunar cycle. They are defined by a prominent 'recumbent' stone, positioned horizontally, so that the moon sets behind it at both extremes of its cycle, and upon which stones cup-marks are often found.

In Aberdeenshire, with a mean latitude of 57° 30's, the moon at its maximum, will rise at 155° SSE, and set at 205° SSW. Of the 48 recumbent's where it is possible to plot their axis, 45 have recumbent between these limits. The remaining were placed at 230°, 231° and 232°, the min moon setting. (Ref: Burl. Stone circles).

It is an interesting fact that the only recumbent circles found outside of Scotland, are in the Ross-Carbery area of Ireland, which places them too far south to make them any use as lunar observatories, and have in fact been shown to be solar in their orientation. Cope (4), makes note of the Drombeg RSC, where the sun has been observed setting at midwinter (solstice), directly into a notch in the landscape behind the recumbent stone.

(Prehistoric Scotland Homepage)

The three Devil's Arrow's (left), are aligned towards the Thornborough Henges (right).

An example of a 'Triple RSC' may be found at Loanhead of Daviot, in Scotland, where the three Neolithic recumbent circles are aligned. The circle in Daviot churchyard was removed in 1820, and all that remains of New Craig is the recumbent, its flankers and a few odd stones now built into a field wall. (4)

(Article - Nov 2009). Oxford: Between the rivers Thames and Cherwell.  A team from Museum of London Archaeology (MOLA) has been excavating parts of the 3.7 hectare site. The excavation has revealed evidence of three large prehistoric 'ring ditches' along with some evidence of possible associated cremation burials.

Stone Quadrangles:

There are a handful of megalithic 'Cromeleques' which whilst retaining an essential geometric design - are not circles. The famous Carnac alignments in France have at one end a stone-circle, and at the other lies a less well known 'cromeleque' which is in-fact a quadrangular enclosure, which has raised debate over the fact that the angle created between the opposite diagonal corners appears to have a relationship to the latitude upon which it sits. While this may at first sound obscure, the 'station-stones' at Stonehenge also form a quadrangle which similarly mirror the latitude upon which it was constructed.

The smaller sides of the Station-stone quadrangle are orientated at approximately  51° 10', which is the same as the latitude upon which it sits.

Although Stonehenge is commonly known for its solar orientation, the original construction has been identified as having had a lunar orientation, and the site was constructed on the exact latitude at which the maximum settings of the sun and moon are at 90° to each other. The same is true for the Crucuno monument at Carnac which was located at the unique latitude on the Earth at which the solstice sun, both summer and winter, form a perfect Pythagorean triangle relative to the parallel of latitude, that is to the east-west, equinoxial axis of the site. In turn, this 3:4:5 triangle is the first of the Pythagorean triangular set.

Quadrangular enclosures at Stonehenge (left), and Crucuno (right).

It is thought that the rectangle of stones (Crucuno), could have been set up for astronomical observations, as not only do the east-west sides align to the equinox sunrise and sunset, but perhaps more importantly, the diagonals align to the both the solstice sunrise and sunset positions, similar to the four 'station-stones' at Stonehenge. It has also been suggested that the positions of various major moon rise and moonset positions are indicated at the Crucuno quadrangle, whose dimensions encompasses an approximate 3:4:5 triangle.

The Xarez cromeleque in Portugal is also a stone 'quadrangle'. Although the original layout of the monument has been questioned, the archaeologist Dr. Pires Gonçalves concluded after several years research on the site that its original design was quadrangular. Perhaps of equal importance is the fact that it belongs to an alignment of sites stretching over 50km, towards the Almendres circle, with an azimuth which closely conforms to the full moon in spring (5).

(More about the Xarez-Almendres Alignment)

Both Stonehenge and Almendres are located on the latitudes of the extremes of the moons 18.6 year cycle, so that it passes directly overhead on its zenith at full moon. In addition, Stonehenge is located on the unique latitude at which the maximum lunar and solar settings are at 90° to each other.