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Penrhiwen

Equinoctial alignments fromLechwedd Penrhiwen, Rhayader, Powys.

The Stone Hand at the Head of the White Water.

			OS ref: SN 932 697 (Landranger sheet 147)

Photograph of the Sun setting at the declination corresponding to the Megalithic Equinox in 1800 B.C. The semi-diameter sits perfectly in the hill notch to the west. This photograph was taken over the standing stone catalogued Lechwedd Penrhiwen. It stands near the mountain road to Aberystwyth about two miles out of Rhayader and is not yet a recognised and protected monument. This is a typical Welsh lechwedd, (stone hand), a long, narrow stone with it's base nearly as wide as it's height. It leans now but the long faces are still aligned both to the west, to the hill junction, as the above photograph shows, but also, in the reverse direction, to the east indicating another hill-flank intersection.

The rising Sun appears first in this eastern hill flank intersection on the morning of the same days as it sets in the hill intersection to the west- Megalithic Calendar intervals 1 & 9- the equinoxes. At the time of this sunrise the Sun's declination was nearly half it's own diameter distant from the ideal required declination for the megalithic equinox. This ideal declination would not be attained for more than 12 hours after the sunrise. For the ancient astronomers to verify that this was the correct day reference would need to be made to the sunset position on the foresight to the west later the same day. This would show them that the ideal position had passed and had been reached sometime between this day's sunrise and set.

To create an observatory where one straight line indicates the Megalithic Calendar equinoctial dates in both directions would not be simple even on a level plain with plenty of room and with both horizons flat. Finding this unique position in such a precipitous landscape is a masterly feat of empiric surveying skills. For digital surveys of these alignments with more recent photographs see html page Penrhiwen2.

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