Banner: Knocknarea sunset
Sunset over Knocknarea.
A dramatic sunset over Knocknarea viewed from the summit of the west cairn on the autumn equinox around 1998.

Astronomy at Cairns Hill

The large neolithic cairns of County Sligo make fine observation platforms with their flat summits and panoramic views across the horizon. The large cairns on Carns Hill are 8 km almost due east of Knocknarea and afford one of the best views to Maeve's mountain. Over the equinoxes the sunsets and full moonsets drop over and behind Knocknarea. On the equinoxes the sun, which is moving very swiftly across the horizon, sets over the ruined neolithic cairn known as Knocknarea South, which has a cruciform chamber within the low cairn.

Equinox sun setting over Knocknarea.
Equinox sun setting over Knocknarea.

The sun drops behind Queen Maeve's cairn approximately 8 days after the spring equinox and 8 days before the autumn equinox. The west cairn being slightly further to the north will have the sun drop behind Maeve closer to the equinox. When you consider that there are five or six monuments on a north south line running through Queen Maeve's cairn, the horizon profile would have had small bumps making notches or measurements on the horizon. This system of observation may have been more concerned with lunar observations, the full moons on or near the equinoxes will also set along this giant calibration.

Knocknarea is a spine tingling place to watch the full moon rise.
Knocknarea is a spine tingling place to watch the full moon rise.

What about looking back in the other direction? The platform summit of Knocknarea is too high to observe objects rising over Carns Hill. The best location for an equinox sunrise observation place is lower down on the shelf on the east side of Knocknarea, where Rathcarrick circle is located. This small boulder circle is a perfect place to watch the equinox sunrises, which come up between the two cairns on the summits of Carns Hill, with Lough Gill beyond.

Coolrea map OSI website.
An excellent aerial image of the Coolrea peninsula from the OSI website. Cairns Hill and Rathcarrick circle are marked.

There is great scope for investigation and research into the sites at Carns Hill and their relationships to the other neolithic monuments on the peninsula. Traffic up and down the river would have passed around the hill. Field work has detected raised platforms running around both cairns. If the trees were cleared both cairns would command extensive views.

Sunset.
Sun dropping behind Queen Maeve's cairn from the west cairn on Carns Hill.

There is another set of alignments to be explored at the solstices; from the west cairn, the winter solstice sun drops into a gap in the Ox Mountains between Doomore and Knocknashee, while the summer sun sets behind the hill of Knocklane.

Range of sunsets over one week at Cairns Hill looking to Knocknarea during the equinoxes.
Range of sunsets over one week at Carns Hill looking to Knocknarea during the equinoxes.

Carns Hill itself is visible from many other sites, and noticably hidden from others

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A dramatic view of the 'paps' at Carns Hill from Google Earth; this is one of many neolithic landscape goddess sites in County Sligo.