Axial stone circle
The stone at the southwest side of the circle, rather than being an upright orthostat like all the rest, is a slab lying horizontally with its long thin edge along the circumference of the ring.
When an observer looks southwest along its axis the midwinter sun can be seen to set behind a notch on the skyline directly over the axial stone.
The locations can be displayed dynamically via the OpenStreetMap viewer (there is an additional multiple-stone circle in County Clare).
Ireland's National Monuments Service, part of the Department of Culture, Heritage and the Gaeltacht, operates a database that includes archaeology sites.
In Ireland, however, the recumbent stone is a somewhat thin slab, quite modest in size, and Ó Nualláin regarded it as lying "upright".
[6] The Scottish circles are arranged so their two tallest uprights (flankers) are on either side of a massive recumbent that weighs up to 30–40 short tons (27–36 t),[16] far bigger than any of the other stones.
[17] The line over the axial stone points southwest and there are some indications that the actual direction depended on topographic or astronomical features, particularly the moon.
They all contained central pits with cremated human bone but there were few artefacts and dating proved very variable.
[23][24] Five-stone circles are small in size – the diameter may be only 2.5 metres (8 ft 2 in) – and they are somewhat elliptical being greater in length along the axis that across it.
[29] Whereas multiple-stone circles tend to be located in low, coastal areas, five-stones are found on higher ground inland.
[32][33] When observing sunrise or sunset Lockyer understood that not only is the apparent movement of the sun across the sky relevant (which depends on the latitude of the observer and the time of year[note 2]) but the altitude[note 3] of the horizon at the point of sunrise or sunset also matters.
It was the only such circle he was aware of outside Aberdeenshire in northeast Scotland and he found the similarity to be remarkable considering how far apart the places were.
Looking towards the southwest across the diameter of the circle and passing centrally over the axial stone Somerville observed a "very conspicuous notch in the hills distant about a mile" at the point at which the sun set at the midwinter solstice.
Barber (1973) discussed the concept of "axis of symmetry" and, after adopting objective criteria for how accurately the azimuth of an axis could be measured and by considering a priori specific solar and lunar situations for rising and setting, he found that 12 out of 30 axial stone circle sites showed acceptable alignments – a statistically significant result.
Alternatively, the stone has been used to indicate a region of interest along the horizon within which to look for landscape features which align with astronomical events.
He considered that archaeoastronomy should be regarded as an aspect of anthropology which helps us in studying ancient people's ways of thinking.
[51][50][18] The axes of the circles are certainly not random: they are almost all aligned between west and south – but further precision and understanding remains elusive.
