of Cairn G incorporates a structure known as a roofbox.
The only other example currently known in Ireland is at Newgrange which is aligned to the winter
solstice sunrise. Another was found in recent years Crantit on the
Orkney Islands, where there are about 80 chambered cairns.
The Carrowkeel roofbox has several features in common with the one at Newgrange.
It is located over the entrance to the chamber; a stone door
is present; and the roofbox admits a beam of light from the sun
at sunset over several weeks on either side of midsummer.
there are also some features about Cairn G which are different
to Newgrange. The passage is much shorter than Newgrange, only
about two meters long, and so the roof box opens directly into
This means that the sun can shine into the chamber
for a much longer period of time than Newgrange - approximately
a month on either side of midsummer, though it only spends about
two weeks in the rear of the chamber.
Also, even though the sun
has been displaced by 1.5 degrees (three solar diameters) to
the west or left, it is impossible for the midsummer sunset to have shone
into the end recess of Cairn G.
what about the moon, which often gets overlooked in preferance to the
sun, as at Newgrange. The full moons rise and set approximately
180 degrees opposite the sun's rising and setting positions. The setting
full moons on either side of the winter solstice will illuminate the chamber
of Cairn G in much the same fashion as the sun does each summer. I have been in Cairn G for several cold midwinter moonsets, but the moon has set in to thick banks of
cloud over the Ox Mountains, too faint and obscure to photograph.
I would imagine that after observing the moonset, the ancient skywatchers
may have stood on top of Cairn K to watch the winter solstice sun rising
over Doonaveeragh and Lough Key. Ritual astronomy undoubtedly played a major role in the design and
location of these monuments. The small stone and chalk
balls were may have been used as teaching aids, held up in the roofbox to show
solar and lunar positions on the horizon to students or initiates. Some
of the finds from Carrowkeel are in display in the National
Museum in Dublin.
The main axis of the cairn and chamber
is aligned to the left edge of Knocknarea with the Great Cairn on its summit. This is a similar axis to Cairns B,
E and K, and is approximately the position of the northern extreme setting midwinter full moon. The lunar standstill occurs
every 18.6 years, when the moon reaches its maximum swing away
from the ecliptic. While plenty of research has been done on
lunar extremes at Stonehenge and Caillinish, relatively little
is known of how Irish monuments relate to the moon.
lunar standstill is difficult to predict precisely and a distant foresight, usually a mountain was preferred.
Knocknarea, which could be translated as The Hill of the Moon is the main foresight
for Carrowkeel, but it is too far to the north for the lunar standstill to reach.
The best candidate is the small cairn on Croghaun in the Ox mountains, which is visible through the roofbox from the back of the chamber. So, when viewed from within Cairn G, the cairn on Doomore marks the midsummer and Croghaun the lunar extreme or 'lunstice' setting positions. It has been suggested that the roofbox at Cairn G was used for predicting eclipses.
Knocknarea is located on the western end of the Cuil Irra peninsula, which could possibly be translated as the 'Remote Angle of the Moon'. The lunar standstill was undoubtedly a great ritual event in a calendar of astronomical observations which were made by our neolithic ancestors. It defines an
axis between the central ridge of Carrowkeel and Knocknarea. Knocknarea
was also used as a foresight from Moytura which is situated east of Carrowkeel across Lough Arrow.
The summer solstice sun drops behind Knocknarea when viewed from
Shee Lugh, the cairn on highest point, which could be called
the Seat of the Sun God of the Túatha Dé Danann.
This cairn is where Lugh Lamh Fada, the young champion and grandson
of Balor of the Evil Eye, sat during the mythical Battle of Maigh Tuireadh. The physical astronomical features
of the Sligo sites, coupled with their mythological associations
opens the way for a broader interpretation of the meaning of these monuments.