This is the eastern blocking stone of the southern double stone row. Great Mis Tor and Little Mis Tor on the skyline ..... the time is uncertain due to the clock being incorrect in the camera:.however, note that the shadow is LEFT of the stone's vertical mid-line at 23 days before the solstice .......
Closer view of the above. There is a similar photograph below taken on 28th December., where the shadow is RIGHT of the stone's midline at 7 days after the solstice. .
Shadow cast from the Row 3 blocking stone (at bottom edge of the photograph) towards the eastern blocking stones, photo at 3.54 pm (25 minutes before 4.19 pm sunset) ...... in view of this being some time before sunset, perhaps the shadow would move across to the other blocking stone? The job needs a team of observers .....
Shadow cast from the large cist south of the southern double row towards the blocking stone of the northern row (digitally highlighted). The blocking stone of the southern row is at the extreme right edge of the photograph. (digitally highlighted). Taken at 4.04 pm (15 minutes before 4.19 pm sunset). Having thought about this photograph and it being 15 minutes before sunset, I have examined the drawing below of the rows and moved the vector to the blocking stone of the south row, where it points quite closely to the solstice sunset, assuming my dimensions are fairly accurate? It is surprising how much the sun can travel across the horizon after rising and before setting. You can't be in all places right on sunset here!
Zoomed view, details as for the photograph above, again at 4.04 pm.
Shadow cast onto the eastern blocking stone of the south row. Taken at 4.17 pm (2 minutes before 4.19 pm sunset). Note that the shadow (now 7 days after the solstice) is slightly to the RIGHT of the blocking stone's vertical mid-line. The light becomes very pink at this time of day. Four Winds car park in the background.
The menhir (enhanced) south of the stone circle aligned with a certain leaning slab, showing sunset. Photo taken at 4.20 pm.
After a quick trot, a view from the western end of the northern row to the western blocking stones of the southern row - the sun is setting over a clump of rushes with the blocking stones of the far row almost hidden - see next photograph .....
Similar photograph to the above taken at dawn on 28th Dec. to show the western blocking stones of the southern row. It indicates that in the preceding photograph the sun set directly over the prominent stone. A week after solstice, this is quite an impressive alignment of stones that were put here 3,000-5,000 years ago to foretell the seasons for the early farmers .....
Zoomed view.
Pre-sunrise, 3rd January 2017, 8.33 am. The near stone is the eastern blocking stone of the northern row; the enhanced small stone in the distance is the eastern blocking stone of the southern row. This view is looking noticeably uphill so that the "ideal horizon" required for the predicted times of sunrise and this must affect the time of the observed rise, making it later than predicted. .
The free compter program, Stellarium, set for the Lat / Long and Elevation of the Merrivale stone rows, with the atmospheric and ground effects included, gave a first time for sunrise of 8.18:12 am and the second time (for complete sunrise) of 8.22:30 am - the sun takes just over 4 minutes to rise, from first to last position below and above the horizon. Why the first part of sunrise below was at 8.36 am, I cannot say.
8.36 am - the sun is just showing a rim of light. It appears to be over the large stone that casts the sunset shadow on the adjacent blocking stone at this time of year. Yellowmead Farm is in the distance, towards the left. I would have expected the position of the sun to have been slightly left i.e. north of this as it starts its progression towards summer, if this was a perfect alignment, unless this is the result of a delayed sunrise time due to the elevated horizon? The ground beyond Yellowmead Farm is about 460 metres (1510 feet) above mean sea level, although the east blocking stones are about 345 metres (1130 feet) elevation so this may explain some discrepancy. But, higher elevations should see the sun sooner?
For curiosity: the Stellarium program shows that sunrise, from first touch behind the horizon, to just above the horizon, takes 4:15 minutes for Plymouth, elevation 54 metres on this dn this date, 3rd January, with an ideal horizon and no ground or atmosphere displayed. The effect of showing the atmosphere is about 4 minutes later, due to refraction. Try with Merrivale Lat/Long Elev 345 metres.
8.37 am - the sun is half above the horizon, glare reduced digitally in the image. .
8.37 am - a general view of the rows in "dawn" sunlight. The big stone is the eastern blocking stone of the northern row. Pew Tor is seen at far left.
Web site for sunrise and sunset times: TimeAndDate.com .
The question has arisen during this exercise as to exactly when are sunrise and sunset? Some information is available on Wikipedia - Sunrise and USNO - Rise, Set & Twilight Definitions. - this includes definitions of Astronomical, Nautical and Civil twilights.
Diagram from
Wikipedia - Sunrise
One definition is "Sunrise is defined as the instant in the morning under ideal meteorological conditions, with standard refraction of the Sun's rays, when the upper edge of the sun's disk is coincident with an ideal horizon.", from Australian Government Geoscience Australia - Astronomical Definitions. If it coincident with an ideal horizon, can you see it or is it still hidden, and if so, how long before it appears?
Answers please, on a postcard .....
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