Cairn S Lughnasa sunset 2

Cairn S at Slieve na Calliagh, Loughcrew, Co. Meath, is a special monument of the New Stone Age. It was built there, part of a substantial complex of cairns, over five thousand years ago. It is one of just three cairns which has a passage pointing towards the western aspect – almost all the others pointing towards somewhere in the east.

For many years, I wondered why Cairn S pointed northwest, in stubborn opposition to the rest. In the early 1980s, Martin Brennan and his team of observers noticed that Cairn S pointed towards the setting sun at special times of the year – at Bealtaine in early May and Lughnasa in early August. These are two of the old so-called 'cross-quarter days', the halfway points (in days) between the solstices and the equinoxes.

But for years, there was something else that captured my curiosity. I knew that Cairn S pointed generally in the direction of Sligo, and for a long time I wondered whether it might point towards any of the cairns of Carrowkeel. In recent years, I read a statement in a paper by an academic scholar on archaeoastronomy that none of the Sligo cairns was visible from Slieve na Calliagh, so the idea that Cairn S pointed to Carrowkeel seemed irrelevant.

However, I needed to find out for myself whether intervisibility between Loughcrew and the Sligo monuments was even remotely possible. In August of 2022, I brought a pair of giant binoculars to Cairn S. Those 25x100 binoculars would, on a clear evening, offer unprecedented and clear views of the distant horizon. Guess what? After a couple of minutes of searching, I could see a cairn on a distant hilltop, barely visible above intervening hills. It was the lone cairn on the mountain of Kesh Corran, just west of Carrowkeel. Bingo! At least one of the cairns of the Carrowkeel-Kesh Corran complex was indeed visible from Cairn S.

Wondering about what this might mean, I could not help thinking that the builders of Cairn S were pointing back to the lands of their earlier ancestors, to the place from where they had come as they journeyed eastward. The distance between the two cairns is 94km (not far off 60 miles). 

Before I knew about the alignment to Kesh Corran, I had made several efforts to capture the setting sun aligned with the passage of Cairn S. As usual, one-off astronomical events in Ireland are often hindered by clouds and weather. On this occasion, cloud covered most of the sky, but there was a clearance near the horizon, so I waited and waited, and eventually the sun dropped below the cloud line and shone into the ancient monument.