Exploring Waterford's Ancient Monuments
Archaeoastronomy at Coumaraglin
In The Bowl Of The Night
Some years ago, the possible relationship between megalithic and other landscape features, and astronomical phenomena, began to be studied seriously, eventually becoming the formal discipline of archaeoastronomy.
Having become interested in the subject, I wondered if there were any interesting alignments in the nearby Comeragh/ Monavullagh mountains.
I chose the Coumaraglin area as potentially interesting, due to the multitude of archaeological sites and features to be found there, as catalogued in the Archaeological Inventory of County Waterford.
I thought that it was reasonable to suppose that, as at Newgrange and other major sites, any alignments would be valid for the important dates on the calendar, the Equinoxes and Solstices. There were quite a few difficulties, however, in figuring out where exactly to look. There are many features in the area, which may be related one to another, but appear to bear no meaningful relationship to horizon events. Also, because of changes in the tilt of the Earth's axis over several thousand years, apparent sunrise and sunset at the solstices have moved along the horizon, so any alignment will not now be exact, making it difficult to be sure whether or not it was intentional in the first place. The deviation is small, about 0.5 degree, (one sun diameter), per 2000 years, (see photo below) but is still very significant. It can be allowed for, yet an element of uncertainty will remain.
It eventually struck me that the Equinox point, being midway between the extremes, would remain the same over the passage of time, and that an alignment on this horizon point could be more reliably accepted.
Using a spreadsheet of astronomical formulae, I was able to determine the position of sunrise on the horizon at various times of the year, taking into account the position of the observer, the horizon height, etc. I narrowed the search using mapping software, (Mapmaker), to compute angles, and an astronomy program, (Cartes du Ciel ), to verify my calculations, and eventually discovered that there appear to be several alignments worthy of serious consideration. I concentrated on the equinoctial sunrise, and found what I was looking for; calculations indicated that the equinox sun would rise over the Bearnanamadra Gap standing stone, viewed from the Carraigaruppera outcrop, which provides a panoramic view of the mountain range.
Next, visual verification was needed, in order to confirm the accuracy of the alignment.
The Bearnanamadra Gap
There is an extensive archaeological complex in the Coumaraglin Valley, at the foot of the Gap. The standing stone (arrowed below) is positioned on a slope close to the centre of the Gap and slightly to the left of the lowest point, for no obvious reason.
Perhaps this suggests it's deliberate placement, as an Equinox marker. The 'backsight' of this alignment would be the Carraigaruppera outcrop, at a distance of approx. 2.5 Km to the west.
Above is the short version of how Mark Chapman and I came to be standing on Carraigaruppera, a natural outcrop surrounded by archaeological features, at 7.30am on the morning of the Autumnal Equinox 2002, waiting for sunrise, and hoping for clear skies. Ice-core and dendrochronological data provide some evidence for warm periods in northern Europe during the 'Holocene Climate Optimum', 9000 to 3000 years ago, so skies may have been clearer when these markers were set up. If so, perhaps climate deterioration was a factor in their eventual lapse into disuse and dereliction. Further research should clarity matters. (Baillie, etc.)]. Good viewing conditions are fairly rare at the present time, being favourable about 1 time in 3.
On this occasion, however, we were not disappointed, as the sun clearly rose behind the standing stone in the Gap. Although the sunlight obscures the stone, we can verify the accuracy of the alignment, leaving little doubt in my mind as to its intentionality. The event is highlighted by the series of photographs below.
Hoping for a break in the cloud cover. Our first exciting glimpse of sunrise, Sept. 21st, 2002
A low bank of cloud obscured the Sun at the moment of sunrise. About a minute after first flash,the Sun's centre is about 0.25 degrees to the right of the standing stone.
After two to three minutes, the Sun is clear of the horizon. It's centre is about 0.75 degrees to the right of the standing stone.
Possible alignments are indicated at other sites in Coumaraglin, and investigation is on-going, as time permits, but for me, a very convincing candidate is the equinox sunrise, as spectacular now, as it was those thousands of years ago.
This article and photos by
Published on PW February 2015
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