Glossary X
At a lunar backsight where permanent or temporary ancillary extrapolation gear has been set up there should be a length preserved between major stones which is the 4G for this site. This 4G represents, on the ground, the lateral distance an observer must move in order to 'shift' the Moon through the declination range K. K is the change in the Moon´s position during the 24 hours preceding a standstill. At a Major Standstill it is 46.5 arc minutes and at a Minor Standstill 30 arc minutes. See also- K, ANGULAR DISPLACEMENT, EXTRAPOLATION PROCEDURE, LUNAR STANDSTILL.

Gop Hill Cairn, Flintshire, North Wales.

y Gop
Gop Hill cairn is considered to be the second largest cairn in mainland Britain. This mound stands on a commanding hill-top position overlooking the Dee estuary and the distant Wirral peninsula.

Evening Sun roll down Glop Hill cairn on 13th April, 2019.

On the evening of the 13th April 2019 a photographic study was secured of the Sun's path on the western flank of Gop Hill cairn. A camera position was found from where the final flash of the upper limb of the solar disc sat on the slope of Gop cairn. Without moving the camera position succesive shots were obtained of the solar upper limb rolling down the entire flank of the cairn.

Gop Hill obliquity Sun roll.


Obliquity on Gop Hill cairn.

Obliquity on Gop Hill cairn.


As with Silbury Hill in Wiltshire, if the northern flank of Gop cairn is symmetrical, and maintains the Angle of Obliquity, it could still function as an universal foresight in support of calendrical and lunar cycle observations.



Silbury Hill backsights.

Solstices, equinoxes and all major and minor lunar limiting positions.



Gop arial alignments.

An Obliquity to the Ecliptic mound: An universal foresight.
As with Silbury Hill, Wiltshire, Gop Hill cairn has been constructed with flanks at precisely the Angle of Obliquity. Hence stances may be found, observing to the cairn's northern slopes, for all rises and sets for both summer and winter solstices, both equinoxes and both Major and Minor Standstills of the Moon.