The sun is now moving onto the sill stone and orthostats in the main chamber, these stones also bear carvings where the sun is travelling.

Carvings normally hidden from view become easily visible on the passage and chamber orthostats.

A narrow beam of light signals the ending of the illumination of the heavily carved backstone, with the unpredictable weather at the time of the equinox in September and March, this could be the last time the sun shines directly onto the backstone for many months, if not years. More often than not, the trek up the mountain in the dark is not rewarded by this fascinating show of engineering and astronomy.

In this photo you can see how the beam is shaped into a roughly square shape, you should be able to make out the symbols carved into the sill stone and chamber orthostat.

The suns rays begins its retreat down the right hand side of the passage, many of the stones in the passage also bear carvings that are easily made out during these last few minutes.

Here you can see just how strong the projected beam is in the chamber. At this point the beam is entirely cast onto stone 6 in the main chamber, it will reach the small circular carving just visible to the top right of the sunbeam before stopping and shrinking from right to left until the chamber returns to gloomy darkness.

A rare fresh, sunny morning at Loughcrew on the eve of the equinox. The ruined Cairn V is in the foreground, a small crowd is still gathered outside the entrance to Cairn T.

Clear skies once again above Cairn T at Loughcrew as the crowd begins to make their way down the hillside.

Cairn T sits quietly waiting for the sun to return again, many months from now.