Ever since I saw the major southern standstill of the moon at Callanish on the Western Isles in 2006 (see my article The Song of the Low Moon), I’ve been wanting to recreate it using  the open-source astronomy program Stellarium. It’s taken longer than anticipated, but that dream has now been fulfilled.

Earlier this year, I was working on a show in Stornoway, and took the opportunity to drive out to the stones one morning when things were quiet. Nobody was about and I had the site to myself. I took GPS readings at the northern end of the avenue of stones and the top of the Cnoc-an-Tursa, the little outcrop of rock to the south of the main circle, so that I would have a baseline to work from. I then positioned myself at the very end of the avenue (the best place to watch the standstill from), and started shooting a panorama. Not two shots into it, a car pulled up in the road at the side of the circle, blocking my view of the Sleeping Beauty mountain range – essential for the panorama as that’s where the moonrise occurs. Disaster! But what could I do? I had to carry on taking the pictures and hope that I could sort it out later on when I was stitching them together to make the panorama.

Well, that turned out to be the easy part of the procedure of making the Stellarium landscape. Far more difficult was getting things to line up properly so that the moon would do what I remembered it doing in 2006. In theory, one can align a landscape panorama pretty accurately from the two sets of GPS coordinates; in practice it usually requires much fiddling in the paint package to get things aligned properly. In this particular case it was even more difficult, particularly getting the horizon height correct, and I have spent many hours adjusting the image by a pixel or two in every direction until the moon’s path at the standstill finally approximates pretty closely to what I remember from 2006.

You can download the Calanais landscape from the Stellarium landscapes page (you’ll also need Stellarium, of course), or from a selection of other stone circle landscapes over at The Geomancy Group. I’d be interested in hearing what you think about the landscape – please leave a comment.

Update October 2010: Ian Pegler kindly sent me this multiple-exposure image of the lunar standstill at Callanish that he made using the Stellarium landscape and the GIMP paint package. You can clearly see how the moon rises from the ‘thighs’ of the Sleeping Beauty and rolls along the horizon, before setting behind the Cnoc-an-Tursa hillock. You can’t see it re-gleaming in the centre of the circle in this picture – you’ll have to try it out for yourself to see that.

Ian has also made some fine landscapes for the program that you can find at the links above. Thanks Ian!