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S2, Llananno to y Glog, Dolfor.

Foresights for the extremes of Cyclic Perturbation at the Northern Major Lunar Standstill in 1800 BC. S2, an isolated stone block carved into a chair.

On the evening of the 18th November 2005 good images of the moon rising at the northern maximum were secured. This photograph was taken from a position behind the stone chair S2, Llananno at about the head height of an observer sitting in the chair. Glog Hill, Dolfor with it's many tumulii is presented across the position of the Northern Major Standstill moonrise. 18th November 2005. Declination = 28* 25.16'.

From the known apparent diameter of the moon at this moment a true mean diameter may be calculated and the track of the rising moon can then be extrapolated along the horizon to show the situation at any time in the past. Cyclic Perturbation markers. The moon in it's orbit exhibits a marked 'wobble' with an amplitude of 18 minutes of declination. At a suspected lunar standstill foresight we should expect to see the alignment catering to one or other, (if not both), extremes of this perturbation. Moonrise with declination 29* 12' = (e+i+p) 1800 BC. By calculated extrapolation along this horizon we see that the track of the rising moon at a standstill in 1800 BC, (e+i), with positive perturbation, (+p), slides up the northern flank of Glog Hill. Tumulii a, b, c, and d are all within two minutes of the declination of the track of the upper limb of the moon. Moonrise with declination 29* 3' = (e+i) 1800 BC. There appears to be no suitable foresights for either upper or lower limb when the moon rises with mean perturbation. Tumulus g is too far from the centre of the disc to be efficient. Moonrise with declination 28* 54' = (e+i-p) 1800 BC. Tumulus f and it's northern flank give the precise declination for the upper limb with the moon at negative perturbation, (-p). We see here that foresights for both extremes of Cyclic Perturbation at the Northern Major Standstill are presented allowing the astronomers to set stake positions which would give an accurate determination of the current condition of this aberration of the lunar orbit.

For further on the potentials of y Glog see: S1, Llananno to y Glog. <<<Home with comments or queries- powys@megalithicsites.co.uk