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.

S1, Llananno to Crugyn Gwyddel, Esgair Pen y Garreg.

The Cairn of the Irishman on the Ridge at the Head of the Garreg,

Winter Solstice alignment from S1 stone chair on Brondre Fawr ridge to Crugyn Gwyddel cairn on Esgair Pen y Garreg indicating the lower limb of the Sun when setting at the winter solstice circa 1800 BC.

Crugyn Gwyddel, Bronze Age cairn, Esgair Pen y Garreg, Rhayader.

S1 Llananno to Crugyn Gwyddel.
This image was obtained by Nikon slr photography.

Crugyn Gwyddel high resolution slr.

As observed today from S1 Llananno this cairn is difficult to resolve with the unaided eye as the Sun no longer sets directly on it.
To be noted is the positioning of the cairn on the secondary peak of the Pen y Garreg ridge. A rocky knoll some 500 meters to the west has a slighty greater altitude- but it was not chosen. An unusual variation from the pattern where a marker would be placed on the summit of a hill. However, when we examine the astronomical potentials of this subsidiary rocky outcrop, where the Cairn of the Irishman has been located, we may see the intent of the constructors.
Several white quartz blocks weighing around one tonne each have been carried to this remote place.
The pile of flagstones, also transported here, may be the ruined walls of a small chamber which had abutted on the quartz boulders.

Digital Survey from a photographic series.

The series of images captured may be layered together to show the exact path of the rising
Warren Hill tumulus sits within an arc minute of the rising point of the Sun's upper limb when it has reached the ideal declination for intermediate megalithic calendar intervals nos. 9.5 & 16.5.
The ideal declination for these dates, (-13 deg. 59.4 mins.), had been attained 47 minutes, in time, before this photograph was taken.

The Green Flash

The legendary green or emerald flash, more halogen blue in this instance, captured on the morning of the 3rd October 2001.
An accurate montage of the solar disc is placed for reference in this image. The disc is some 31.6 arc minutes in diameter. Notice how the flash appears magnified. This photo was taken only two seconds after first gleam was visible when the rim of the disc must only be a few arc seconds over the horizon- yet the green flash stands several arc minutes clear on the hill- top.
When half- risen the diameter of the disc fits exactly between the tumulus and the intersection of the hill flanks. With this arrangement estimates of the proximity of the ideal moment that the required declination had been, or would be, attained might be made.
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