12th January the sun is setting further north, but it still shines down
the passage. It first illuminates the back wall
By mid-January the sun still illuminates the chamber. First the a narrow beam of light shines along the floor and finally just reaches the back wall, and illuminates a "letter box" shape to the left of the blocking stone. This beam moves towards the right and upwards, and is finally then extinguished as the sun disappears behind the Ward Hill of Hoy. On 12th January the beam from the north side of the Ward Hill lasts from over five minutes, but there is an earlier day when it lasts only a very short time - the so called "flashing" effect. We hope to determine which day this occurs this year - weather permitting. We had great success on 1st December 1998 and 11th January 1999.
As the sun sinks lower the light fades and the patch of light moves to the right across the blocking stone. Because thesun goes further north before dipping behind the Ward Hill, the patch moves further right each day.
At approx 15:20 GMT the beam reappears on the right hand side of the blocking stone. Because the sun is now lower in the sky the patch is higher than earlier on. An irregular patch of light appears on the wall, caused by the outer end of the passage, moves right and then disappears at 15:30. By 15:35 the sun has disappeared from the passage also.