2018 Moon Phases for Stonehenge. #FullMoon #Calendar

14 01 2018

Ancient peoples had the benefit of dark skies and experienced the full spectacle of the starry heavens. The Moon gave light at night and would have been particularly useful in the two weeks centred on full Moon. The regular monthly cycle of lunar phases provided a convenient measure of time, upon which many ancient calendars were based.

Was it a Neolithic calendar? A solar temple? A lunar observatory? A calculating device for predicting eclipses? Or perhaps a combination of more than one of these? In recent years
Stonehenge has become the very icon of ancient astronomy, featuring in nearly every discussion on the subject.
A more informed picture has been obtained in recent years by combining evidence from archaeology and astronomy within the new interdiscipline of archaeoastronomy – the
study of beliefs and practices concerning the sky in the past and the uses to which people’s knowledge of the skies were put.

Lunation New Moon First Quarter Full Moon Third Quarter Duration
1175 2 Jan 02:24 8 Jan 22:25 29d 19h 47m
1176 17 Jan 02:17 24 Jan 22:20 31 Jan 13:26 7 Feb 15:53 29d 18h 48m
1177 15 Feb 21:05 23 Feb 08:09 2 Mar 00:51 9 Mar 11:19 29d 16h 06m
1178 17 Mar 13:11 24 Mar 15:35 31 Mar 13:36 8 Apr 08:17 29d 12h 46m
1179 16 Apr 02:57 22 Apr 22:45 30 Apr 01:58 8 May 03:08 29d 9h 51m
1180 15 May 12:47 22 May 04:49 29 May 15:19 6 Jun 19:31 29d 7h 55m
1181 13 Jun 20:43 20 Jun 11:50 28 Jun 05:53 6 Jul 08:50 29d 7h 05m
1182 13 Jul 03:47 19 Jul 20:52 27 Jul 21:20 4 Aug 19:17 29d 7h 10m
1183 11 Aug 10:57 18 Aug 08:48 26 Aug 12:56 3 Sep 03:37 29d 8h 04m
1184 9 Sep 19:01 17 Sep 00:14 25 Sep 03:52 2 Oct 10:45 29d 9h 45m
1185 9 Oct 04:46 16 Oct 19:01 24 Oct 17:45 31 Oct 16:40 29d 12h 15m
1186 7 Nov 16:01 15 Nov 14:54 23 Nov 05:39 30 Nov 00:18 29d 15h 18m
1187 7 Dec 07:20 15 Dec 11:49 22 Dec 17:48 29 Dec 09:34 29d 18h 08m
* All times are local time for Stonehenge. Dates are based on the Gregorian calendar.
Source: Time and Date

Stonehenge Links:

Astro Moon Calendar shows phases of the Moon each day, astronomical events and astrological forecast for the year.
Stonehenge and other stone monuments were probably used for special moonlit ceremonies.
Stonehenge and Ancient Astronomy. Stonehenge and Avebury World Heritage Site
Stonehenge Full Moon Guided Walking Tours.  Explore the landscape with a local historian and astronomer.
All eyes on the sky! We’ll see a supermoon, blue Moon, and blood Moon all in one night!
How to see the super blue moon, a cosmic event you won’t want to miss

The Stonehenge News Blog
Follow us on Twitter and Facebook for daily Stonehenge Sunset / Sunrise / Moonrise / Moonset times.

 





Stonehenge – Eclipse Predictor?

4 01 2017

Astronomer Prof. Gerald Hawkins wrote two articles for “Nature” in 1963 and 1964 in which he pointed out several new Stonehenge alignments to the Sun and Moon and proposed that the 56 Aubrey Holes could be used to predict eclipses. His subsequent popular book “Stonehenge Decoded” gave the world the idea that the monument was a Neolithic computer.

stonehenge-decoded-and-gh

Archaeologists were horrified at the thought and the leading authority on Stonehenge at the time, one Richard Atkinson, wrote a rebuttal paper in 1966 called “Moonshine on Stonehenge” which heavily criticised Hawkins conclusions. Atkinson considered the builders of Stonehenge to be “howling barbarians” – a statement he later came to regret.

on-stonehenge-and-fhProf. Fred Hoyle followed up Hawkins’ work on the eclipse predictor idea and came up with a relatively simple recipe for moving markers around the 56 Aubrey Holes to keep track of the Sun, Moon and the two points in the sky where their paths cross (the “nodes”). He published this work in two journal articles in 1966 and then in his 1977 popular book “On Stonehenge”.

 

So how does this eclipse predictor theory work and is it possible that the Aubrey Holes were in fact used like this? We’re going to have to get slightly technical, but it’s not too hard to follow.

Hoyle said that you need a marker for the Sun, one for the Moon and two more for the “nodes”, and that these markers are moved around the 56 holes of the Aubrey Hole circle in a particular way.

The Moon goes around the Earth once in about 27.3 days (the “sidereal month”) so if you move your Moon marker two Aubrey Holes per day it’ll go once round the circle in 28 days.

The Sun goes around the entire sky once in about 365.25 days (the “tropical year”), so if you move your Sun marker two holes every 13 days it’ll go once round the circle in 364 days.

The points where the paths of the Sun and Moon appear to cross (the “nodes”) also gradually move around the sky, taking 18.61 years to make one revolution. This period is called “the regression of the lunar nodes” and occurs because the Moon’s orbital ellipse actually rotates slowly around the Earth.

The Moon’s orbit is also tilted by about 5° to the path of the Sun in the sky, which is why we don’t get eclipses every New and Full Moon – we only get eclipses when both the Sun and Moon are at or very near the “nodes”.

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The node markers are always kept opposite each other – there’s the “ascending node” and the “descending node” – one for each of the two crossing points on opposite sides of the sky.

To keep track of the nodes, you move their markers 3 holes each year – in the other direction to the movement of the Sun and Moon markers. This means the node markers go backwards round the circle once in 18.66 years.

To summarise:

Arbitrary Position and Explanation.png

Now, 28 isn’t 27.3, 364 isn’t 365.25 and 18.66 isn’t 18.61 but the inaccuracies can be corrected.

Every month you can fix the Moon marker by making sure it’s in the Aubrey Hole directly opposite the Sun at Full Moon.

Twice a year, at the solstices, you can make sure that the Sun marker is in the Aubrey Hole closest to Stonehenge’s main axis – either the Aubrey Hole towards the Heel Stone at summer solstice or the one directly opposite it across the circle at winter solstice. The error between 18.66 and 18.61 is actually small enough not to matter.

Suppose you see a lunar eclipse one night, this allows you to set up the markers in the first place. The Sun and Moon markers are placed directly opposite each other (because lunar eclipses are only possible at Full Moon) and the node markers are placed one each in the same holes as the Sun and Moon markers.

Now you follow the recipe for moving the markers, day by day.

If you ever end up with the Sun and Moon markers in the same hole together, and they’re in the same hole as (or in the hole next to) a node marker then this predicts a solar eclipse. Sun and Moon markers in the same hole means New Moon, and solar eclipses are only possible then.

The following animation shows how this works, starting with the solar eclipse of March 20th 2015 and predicting the subsequent lunar eclipse of 4th April 2015.

ah-animation

If all this seems very unlikely and complicated to manage, then you may be right. Hawkins’ and Hoyle’s theories simply show how a 56 hole machine with four markers could be used to track the things that allow you to know when to expect an eclipse to occur.

One of Atkinson’s objections was that if 56 was a useful number for eclipse prediction in the ancient world then it’d be found all over the place – not just at Stonehenge. What’s more, up until the 1960s the number 56 wasn’t associated with eclipse cycles by astronomers.

Curiously, it was discovered later that perhaps the ancients did link 56 with eclipses. There is a passage in Plutarch’s “Of Isis and Osiris”, dating to the 2nd Century AD, which says:

“The Pythagoreans also clearly believe Typhon to be a daemonic power… the 56-sided polygon is said to belong to Typhon, as Eudoxus [Greek astronomer c.370 BC] has reported…

There are some who give the name Typhon to the shadow of the earth, into which they believe the moon falls and so suffers eclipse…”

The argument continues even 50 years on – the builders of Stonehenge clearly weren’t “howling barbarians” and the builders of that monument and others definitely paid attention to the sky and how things moved around it.

Humans have been curious for as long as we’ve been humans and the earliest artifact that has a record of the phases of the Moon on it is a carved bone from the central European Aurignacian culture which is about 32,000 years old (https://sservi.nasa.gov/articles/oldest-lunar-calendars/)

Perhaps we’re still underestimating our ancestors’ abilities, despite the evidence they’ve left behind.

Article by guest blogger and local Stonehenge historian Simon Banton

Stonehenge guided tours are considered the leading Stonehenge experts and offer a range of guided tours including Full Moon and Eclipse Tours, many taking you into the inner circle at sunrise or sunset. Private Stonehenge tours with a Stonehenge expert and astronomer can easily be arranged.

If you want to here more about Stonehenge and the astronomical calendar you could join a Stonehenge walking tour with a local Archaeoastronomer who offers amongst guided walks, talks and even full moon tours.

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