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Step-aside distance between S1 and S2, Llananno to y Glog.

Angular displacement between S1 and S2, Llananno to Glog Hill, (y Glog), Dolfor. At a Northern Major Lunar Standstill.

S2, Llananno.

S1, S2, Llananno Parallax Calculator. S2 is a 3/4 ton earthfast block carved to a rough semblance of a chair. When seated in this seat an observer is presented with a view, to the north west, of y Glog, a steep sided hill near the village of Dolfor, Montgomeryshire. This hill's long crest is adorned with many fine examples of Bronze Age earthen tumulii. Nine are readily discernable today and several more may have been ploughed over. This is, perhaps, the largest Bronze Age cemetery in Wales. From the stone S2 the hill y Glog is 5.5 miles (8.8 kilometres) distant and lies across the path of the rising moon when at the Northern Major Standstill circa 1800 B.C.

Twin camera images of moonrise on the 18th November 2005.

At the lunar extreme of 18th November 2005 two long-exposure shots of the moonrise over y Glog were secured from two cameras positioned exactly 100 metres apart. Camera A was placed behind S2.

S1, Llananno, is another carved stone chair weighing around 2 tons. S1 lies 223.86 metres to the north of S2.

On the line S1 to S2 extended camera B was placed exactly 100 metres beyond S2. S2 is 8 metres higher than S1 and camera B position is another 2 metres higher than S2.

Angular displacement, between S1 And S2. (Step-aside).

Glog Hill is no longer visible from S1 due to tree growth. Simultaneous images taken from the two measured camera positions gives precise measurement of the step-aside distance, in metres, for the angular displacement of the moon on this horizon.

	From camera position B, 100 metres south of S2.

Cameras A plus B images. With the two images layered together we have the angular displacement of the moonrise for a step-aside of 100 metres. From these photographs, taken simultaneously 100 metres apart, the angular displacement supported by moving between S2 and S1 may be calculated. Distance from S1 to S2 is 223.86 metres = 270 Megalithic Yards. Parallax calculator. The lines in red are the tracks of the upper and lower limbs which have a slightly different declination than the 'shoulders' of the moon. In this graphic survey the lunar track has been corrected to mean diameter and for the difference in altitude between S1 and S2. We see the close correspondence between the upper and lower limb tracks- within 1 minute of declination. The angular displacement between the two stones is precisely one lunar diameter with the moon at mean parallax. The positioning of the two stones is carefully arranged so that two observers, sighting to the same point on the horizon, may locate stake-setting positions which would allow close estimation of the condition of the parallax cycle at that moment. Understanding and measuring current parallax is vital at a lunar extreme observation in order to eliminate to mean the true diameter of the lunar disc.

S1, Llananno.

S2, Llananno.

S1 to S2.

For further on S1 and S2, Llananno to y Glog, Dolfor lunar standstill alignments see: S1 to y Glog. and S2 to y Glog.

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