Megalithic Astronomy

big megalith
Whilst I was still at school I became interested in what has been described as "megalithic astronomy" - the astronomy of standing stones. This had been taken forward with some complexity by Prof. Alexander Thom, an Engineering professor in Oxford. My interest was initially as a result of seeing a television programme about his work on the subject - I eventually tracked down that it was a "Chronicle" programme, Cracking the Stone Age Code, shown in 1970. There's a recent commentary on Prof. Thom here.

I even remember talking about my fascination with this when I had my entrance interview at Trinity College - I had already visited and taken notes and simple survey information at a few sites in North Wales.

At Cambridge I met a few other people in CUAS interested in this fascinating subject - was there any basis for Thom's ideas about complex astronomical functions of the megalithic sites, or not? By the end of my first year we had organised a little expedition to the Kintyre area in Scotland, and Douglas Heggie, then a fellow of the college and also interested in the subject, suggested that we do some real surveying. We borrowed a theodolite from the Engineering department, and it took off from there!

Our first expedition resulted in a real scientific paper, "Survey of three megalithic sites in Argyllshire" - we submitted it to Nature and amazingly it was accepted, published and even made the cover! Those were the days of typed manuscripts and hand drawn illustrations which I made using indian ink and tracing paper.

We had a lot of fun with the expedition and the success with the paper, so further expeditions followed. I missed the one to Mull because I had to sort out problems relating to my PhD studentship for the following year - but joined the expedition to Lewis and Harris later in the summer, when we proposed to work on the sites around Callanish. We were never really interested in Thom's ideas about the "megalithic yard" as a unit of measurement; it was the astronomical connection that fascinated us.

Callanish 1975

My photos from the Callanish trip are in black and white - I used to do all my own processing in those days, and we wanted prints to tie in with surveys of horizon profiles. Home processed black and white was also a lot cheaper than colour slides. There was no shop and tourist stuff in those days - though the site was visited by quite a few people during the time we spent surveying.

Callanish stones

For some reason we went through a lot of "brown sauce" at the Laxdale camp site where we were camped for the trip - hence this photo I suppose.

Daddie's sauce

The weather was not always beautifully sunny, but provided the horizon was clear we could survey horizon profiles. The umbrella is more for the protection of the theodolite rather than the surveyor!


We wanted to be able to discover if our surveyed horizon profiles could have been used for astronomical purposes. This meant that we needed to know the azimuth of our surveys accurately, and we relied on solar observations to determine this, in conjunction with an accurate time (from the 60kHz signal then transmitted from MSF Rugby). Guy G3ZHL built the time signal receiver.


Here's the theodolite being used to project an image of the sun, together with the crosshairs, and a stopwatch held ready to catch each limb of the Sun crossing the wires. The time was checked immediately afterwards using a 60kHz receiver for the time signal service.

We didn't just do surveying - we managed to tour around Lewis and Harris, visiting Carloway Broch, and did an ascent of Clisham in the mist. We also did a long walk in to Rainigadale, Harris - in those days there was no real road in to the settlement.

The survey results for this expedition were published as a paper in the Journal for the History of Astronomy, "Indicated declinations at the Callanish megalithic sites". This didn't include the drawings of the surveyed profiles, but I do still have a copy of them.

The Uists 1977

Windy surveying

This was a good follow-up to the Callanish expedition - lots of surveying, though rather more of a holiday. Look at the prone bodies in the photo above - and it looks as though the wind is even blowing the stone over! The weather was extremely windy at times - one rather flimsy "Mediterranean" style tent collapsed in a gale overnight. We had some interesting experiences from Callanish and its surrounding sites so made sure that we had permission to survey in lots of remote places.

Expedition photo

Here's the expedition photo.

Islay and Jura 1978

Islay campsite

Islay is extensively farmed, with big estates, so a lot of effort went into contacting factors to get permission to survey. No wild camping either here - our tent village was on a little camp site complete with touring caravans. By this stage I had my radio amateur licence as GM8OTI, so we were able to use radio communications over sight lines using a couple of portable 2m FM sets I had built. The GM3ZHL HF antenna mast is visible in the photo above. As well as visiting Islay and surveying sites, we made a trip over to Jura, principally to make an ascent of the Paps of Jura.

Expedition photo

Another expedition photo. Lots of people there for the holiday, as well as the keen surveyors!

We had a lot of fun with the megalithic astronomy expeditions, they made great holidays in lovely areas with fantastic scenery. We went our separate ways in our chosen careers (mostly in astronomy) and only Clive Ruggles eventually turned the subject into his job! The work on the Uists and Isaly and Jura wasn't wasted, Clive pulled it all together in a big collection of the work done across western Scotland, and published in the BAR series in 1984.

Later ...

Loch Nell

The stones are still there - this is the big menhir at Loch Nell near Oban, one of the sites surveyed for our first paper; a burial cairn is in the foreground. I took this photo many years later, when we had a caravan near Oban.


Eventually I also managed to visit the stone alignments at Carnac in Brittany. These are so spectacular - the enormously long avenues of hundreds of stones are quite different in scale to the Scottish sites.

Alexander Thom's books

The books that really got me interested in the subject were published a long time ago:

Megalithic Sites in Britain, Oxford, 1967
Megalithic Lunar Observatories, Oxford, 1971