Why did our foremothers and forefathers know so much about astronomy? First of all, unlike ourselves, they lived in it. Anyone who has lived outdoors for a while begins to develop a different relationship with nature and the sky. Living in houses and especially in cities, where the ambient light and the tall buildings block out the heavens, we have forgotten the natural flow of the cosmos. Outdoors, if you get up at first light and go to bed when it gets dark, you notice the Sun as it rises and sets each day. In the Northern hemisphere, over the months you see the Sunrise moving along the Eastern horizon from the North-East at Summer Solstice (the longest day of the year), to the South-East at the Winter Solstice. Likewise, at Sunset, you would see the Sunset also moves along the Western horizon over the year as well.
This is a copy of a Druidic Cross that was given to me by the Welsh Druid Ray Kerley when I lived in Glastonbury, England in the mid-eighties. It was Ray's family's druidic Cross.
From an astronomical point of view, the four arms represent:
The four Quarter Days of the yearly cycle
Winter Solstice - around December 21st (on the cross above: at 6:00 o'clock)
Spring Equinox - around March 21st (at 9:00 o'clock).
Summer Solstice - around June 21st (at 12:00 o'clock)
Autumn Equinox - around September 21st (at 3:00 o'clock)
But the Celts (pronounced "Kelts"), the people of Iron Age Northern Europe were interested in the days half way between these Quarter Days. These Cross-Quarter Days were the major feast days of the Celts. They are represented by the four black balls at the points where the two arms Cross on the Cross shown above.
Samhain - around November 1st, the Celtic New Year (The black ball at 4:30 o'clock - between Autumn Equinox and Winter Solstice)
Imbolc - around February 1st, the quickening (The seed planted at Samhain moves for the first time (the black ball is at 8:30)
Beltane - around May Day, May 1st, the Cross-quarter day of fertility (The crops are up, let's work for their fertility (the black ball is at 10:30)
Lughnasad (Lammas/Loaf-Mass) - around August 1st, the first harvest of the grain (ground into the first loaf of bread of the season for Loaf Mass/Lammas (the black ball is at 2:30)
In looking at orientations, in addition to those of the Quarter Days, some sacred sites on both sides of the Big Pond are oriented towards these Cross-Quarter Days.
Here's an example from Northern Vermont, USA. The picture was taken inside an underground stone chamber.
Cross Quarter Day - Imbolc - Sunset Rodwin Chamber, Northern Vermont, USA.
Notice the Sun is headed towards the notch in the horizon.
The Cross-Quarter Days
The Quarter Days of the year (the Solstices & Equinoxes) can be defined with extreme accuracy - to the nearest nano-second if necessary. The Cross-Quarter Days are somewhat more movable.
The Druidic Cross to the left indicates the Quarter Days with the four arms of the Cross. The Cross-Quarter Days were symbolized by the four much smaller dots in the crotches of the Cross. This would make it seem that they are evenly spaced around the eight-point year. They are in time - but not in space.
Calculating the Cross-Quarter Days
Go to the point on your Orthographic Projection of 51° and locate the declinations of the Summer and Winter Solstice Sun at noon (shown in gray in the illustration).
In half the number of days between the Spring Equinox and the Summer Solstice, at Beltane, around May 1st, the Sun has moved approximately 71% of the distance between these two points on the horizon. 71% of the 23.5° declination of the Summer Solstice Sun would put the Beltane (and Lughnasad) Sun at a declination of +16.6°, and the Samhain and Imbolc Suns at a declination of -16.6°
With your circular protractor, measure 16.6° above and below the declination of the Equinox Sun. Connect the two points, and mark the intersection with the Equinox Sun's path (E2). Put the point of your compass on E2. Your pencil should hit both the +16.6° and the -16.6°.
Without moving apart the arms of your pair of compasses, put the point of your compass on C and swing an arc through the latitude line, finding points B/L2 and I/s2.
Extend a line from BL1 through BL2 to the point where it breaks the level horizon N-C-S at B/L3. Extend a line from I/s1 through I/s2 to the point where it breaks the level horizon N-C-S at I/s3.
Connect B/L3 and B/L' with a straight (transfer line). Do the same with I/s3 and I/s3.
Now, just as we did with the Solstice Sun, let's move into the next dimension:- what does this look like from above? Put the point of your pair of compasses on C, and make short arcs through B/L3 and I/s3.
Without moving the arms of your compass, put the point on C', and make arcs that break the lower N-C'-S line at B/L' and at I/s'.
Draw lines B/L-I/s and I/s-B/L. They should intersect at C'. When viewed from C' this will give you the Cross-quarter day Sunrises and Sunsets at a latitude of 51o.
These are the azimuths of the four Cross-quarter day Sunrises and Sunsets at a latitude of 51°, given a level horizon. You would measure these angles (taken in a clockwise direction from North) using as large a circular protractor as possible.
Up until now, we have been assuming that there is a level horizon. This fixes the Sun in two dimensions. In reallity, the horizon is usually elevated, which adds a third dimension.