Astronomy at Cairn L
The most unusual aspect of this wonderful monument is the presence of a tall pillar stone within the chamber known as the Whispering Stone. This slim striking limestone pillar, rectangular in section, is over 2 meters tall. You gets the impression that the chamber and cairn were constructed especially to house this stone, and as Cairn L seems to have been built after it's satellites, perhaps the Whispering Stone was free-standing for many years. The only other known example of a standing stone within a neolithic chamber of this type known so far is the buried stone within Cairn F at Carrowkeel, which is oriented due north.
The mystery of the Whispering stone is added to by the orientation of the chamber. There is a skew or slight bend in the remaining section of the passage of Cairn L. There seem to be several meters of passage missing up to the modern reconstruction from the 1940s. Standing in the back recess, the chamber seems to be aligned to a notch between two distant hills between Carnbane and Sliabh Rua, well to the left of the alignment illustrated below. The alignment of this passage may have been altered a few times before it was destroyed.
During their research at Loughcrew, Martin Brennan and Jack Roberts discovered that the sun illuminates this chamber on the mornings of Samhain and Imbolc, during the first week of November and the first week of February, the ancient cross quarter days. Though this may not be the original alignment we are still left with a spectacular display.
Trial excavation or resistvity surveying in front of the entrance for empty sockets could tell us how the entrance looked before it was damaged.
As the sun rises over Sliabh Rua, which is also called Carrick Breac - the Speckled Rock, the beam flashes dramatically into the chamber and strikes the top of the Whispering Stone. As the sun rises higher in the sky, the beam of light slips off the standing stone and into the large right-hand recess, which contains the massive basin and a finely decorated chamber stone. The beam of light is very bright in the darkness of the chamber and brilliantly illuminates the engravings - see photographs below. It would seem that the monument and chamber were constructed around this mysterious stone.
Brennan and Roberts also observed the full moon entering and illuminating the end recess of Cairn L on the 26th August 1980. The moon struck a cupmark on the endstone, and then moved to the right to illuminate the bottom of the Whispering Stone. Little observational research has been done on the movements on the moon in these monuments.
The photographs below, part of a sequence taken on a very cold November morning show something of the movement of the Sun within the right hand recess. Sequence of sunbeam within chamber of Cairn L, 8 November 1995. The light source it the sun, canon slr, no flash, fuji slide film.
This monument has been closed to the public for a number of years now, and I believe that this sequence of images is one of the few that exist documenting this amazing alignment. To view the chamber of Cairn L, special permission is needed from the landowner and the OPW.