Posted 30-10-2020 at 19:17
To get back to basics of the lunar standstill, I was asked this question today:
I'm just wondering whether you can recommend a book or article that explains the lunar standstills really well – not just in the context of Callanish? I just can't get my head around them, ie how they're seen on the ground and the evidence for how megalithic monuments tie into them.
For example, are the extreme lunar positions noted for a day, or several days, or even months at a time? Is there anywhere apart from Callanish where they appear to have impacted on a structure's construction?
Everything I see online is insanely complicated with azimuth charts and what not, I would just like a simple explanation in ordinary English! Would be brilliant if you could recommend anything ... thank you!
Posted 30-10-2020 at 19:20
This was my reply. I know simplicity is not always prized in this forum but any advances on this very welcome:
Essentially they work like solstices do for the sun, but whereas the sun reaches the solstice twice a year, at midsummer in June and midwinter in December, lunar standstills follow an 18.6 year cycle, where 2006 was the year of the Major Standstill and 2015 the Minor (when the moon rose at its least northerly and set and its least southerly point).
The effect is most pronounced at higher latitudes, which is partly why it’s effective at Callanish. But It’s also been observed in Chaco Canyon - there's a longer description here which is worth a look.
https://www.umass.edu/sunwheel/pages/moonteaching.html
Posted 30-10-2020 at 20:11
Not sure if it's any use Andy, but needed to explain lunistice for a small section in one of the book's new chapters. Here's that section:
Posted 31-10-2020 at 22:41
Tricky one to explain. The moon's declination will vary over time around its orbit going from -23.5 to + 23.5 degrees (earth's tilt) but plus or minus up to 5.14 degrees due to inclination of the moon's orbit. The moons orbit precesses around in a 18.6 year period thus the declination maximum declination varies from about +-18.36 to +-28.64 degrees.
The moon also has a 28 or so day period, so in practice, rarely reaches the maximum while at the horizon as it goes from maximum to minimum over half of this time (14days). From observing the days on either side of the maximum, it is possible to work out when/where the maxima would occur.
Anyway, coming to the question, there are many sites in the UK where this things potentially could have been observed including some of the following:
From Mull:
Gruline 2 - ~132.5 degrees -e+i moon rise above the large Carn Ban cairn [URL=http:/https://www.megalithic.co.uk/article.php?sid=23079/]Carn Ban[/URL] where the moon just peeps out, then is hidden and later reappears. The stone and Cairn are well laid out so probably not accidental.
Tirghoil - +e+i Moon Rise around 135 degrees - it rises, then goes behind Bearraich to shortly later reappear.
Cillchriosd - about 31 degrees, +e+i Moon Rise. it again just peeps out, then goes behind Beinn na Seilg to shortly later reappear.
From Anglesey:
Castell Bryn Gwyn - about 129degrees rise of -e+i moon above Snowdon. The only known probable Henge on Anglesey and the rise would date the henge to around 2500BC.
Trer Dryw Bach - Moon -e+i about 129 degrees and -e-i about 151 degrees. The rise is above Garnedd Ugain (Just north of Snowdon). (This is using the Burl location for the circle).
Posted 01-11-2020 at 07:02
Understand what you're saying David, but worth bearing in mind that the apparent movement approximates to a sinusoidal motion: So your chances of observing a maximum at the horizon are much increased.
Posted 04-11-2020 at 20:27
The simplest explanation I can give of just the observational basics is that the moon has a northern and southern standstill each month just as the sun has a northern and southern solstice each year.
Over 18.6 years the monthly maximum rise/set positions of the moon to the north/south go through a period when they are less than where the sun rises/sets at the solstices, then passes through the same positions as the sun at the solstices (as it has been doing this year) until it reaches positions beyond that of the sun at the solstices.
Although there is one absolute maximum north/south rise/set position, and catching the moon at the highest values on the local horizon is rare, for many months around Major Standstill the monthly rise/set positions of the moon will swing back and forth between what is more or less its overall maximum positions before that range begins to lessen again through the solstice positions and finally back to the minimum monthly range which is less than solstice positions (minor lunar standstill).
Posted 05-11-2020 at 14:30
Andy you need to distinguish ‘lunar standstills’ which are usually talked about in regard to the 18.6 year cycle of the tilt of the moons orbit round earth, and are nothing to do with solar ‘standstills’ which occur 2x a year. The equivalent for the moon is called a lunistice and is every month. The lunar 18.6 year 'standstill' occurs over a prolonged period of many months, up to a year within 1 degree if i remember right. When the orbital tilt is 5 degrees- with the earths tilt the moon’s elevation goes from very high to very low over the month. Every 9.3 years the moons orbit matches the solar plane and the lunistices match the sunrise/set positions (for a few months)
You belong to academia .edu and you might like to read my paper on this i put up 18 months ago, and you haven't read yet. See page 5 for the lunar cycle. cheers drolaf
Cardinality in the British Neolithic: a geocentric astronomy primer, 2019
Posted 06-11-2020 at 13:13
Best to get the definitions stated:
Lunation = Lunar Month = Synodic Month
This is related to the PHASE of the Moon and currently has a "mean" period of 29.53059 days between two successive New Moons.
The "mean" aspect is important because the actual period for any month varies with so many different astronomical parameters being involved. The mean period can be taken to apply to any two successive phases.
Lunistice
The Moon's farthest north and south points during it's monthly cycle. This is related to the Moon's sidereal period of 27.32166 days. Therefore, there are two "lunistices" every month at 27.32166/2 days = 13.66 days, but the phases will be different.
You won't find this term in an astronomical dictionary! But you will in general word dictionaries (at least online) and wiki, as it's become common "language" since Alexander Thom hit the scene, so to speak.
Altitude This is the correct astronomical term for the angular distance of a celestial object, above or below the horizon.
You won't find "elevation" in an astronomical dictionary as an astronomical term. You will find it, here and there, as an "explanation" of altitude, i.e. = the angle of elevation to the said celestial object. You can argue until the cow's come home, but "altitude" is the correct astronomical term in use.
Having said this, rather than observation at the horizon, the situation at culmination, i.e. on the meridian, might illustrate better for some, as per my graphic below, which I've posted elsewhere in the past:
"Culmination" is the point in time when a celestial object lies exactly on the observer's meridian (north-south line).
So now the 18.613-year cycle:
This is the Lunar Nodal Cycle, full stop! It is measured by the lunar sidereal period, and is the time period between the maximum northern and southern "lunistice" point that the Moon reaches (Major Standstill)OR the minimum northern and southern "lunistice" point that the Moon reaches (Minor Standstill).
It is at major and minor "standstills" - not in any astronomical dictionary except in the context of particular stars - that the Moon reaches maximum and minimum altitudes above the horizon.
Some "curiosities".
Given the above, and the relationship to the Moon's sidereal period for the Lunar Nodal Cycle:
(18.613 x 365.25636 - Earth's sidereal)/27.32166 = 248.832. This answer x 100 = effectively the Earth's circumference at 24884 miles, as argued by ancient metrologists.
(Currently 24,818 miles Polar, 24,901 miles equatorial)
This means that there are twice the number of "lunistices" in every lunar nodal cycle, i.e. 498 rounded.
The number of solstices in every lunar nodal cycle is 37 rounded.
Now you have two numbers. Experiment with them and you'll find that it will confirm, yet again, that ancient metrology is based on astronomy, geometry, number and maths. The answers you get are not "coincidences", nor number-crunching to get what one desires. They are the consequences of a holistic approach, the original "one theory of everything", put together by sophisticated minds, which we "advanced" people, led by our scholarly "experts", dare not attribute them with. They were the "polymaths" which current scholarship still has a long way to go to even get close to matching.
[ This message was edited by: Orpbit on 2020-11-06 13:22 ]
Posted 06-11-2020 at 20:29
That's OK, and the emboldments weren't meant in any disrespectful way. I was having a dialogue with a scholar from eastern Europe and he argued about something, which is irrelevant here, and ended by saying - paraphrasing, "you Brits can't even get 'altitude' right, it's 'elevation'!
Such is life - perhaps they have a different dictionary to ours. But then I can't claim to get everything right, and I think I'm right in general terms with what I've said. But there's always someone round the corner who'll correct me if I have erred!
Astronomical terms, never mind the actual astronomy, can be (is!) very confusing at times.
Posted 07-11-2020 at 17:01
Brilliant graphics Richard. Great explanation for anyone interested in visualising and understanding the moon's 18.61 years cycle. Much appreciated.
Posted 07-11-2020 at 23:01
AndyB
Sorry I missed your post of 30/1020 "I'm just wondering whether you can recommend a book or article that explains the lunar standstills really well".
Yes I can, it is 'Sun, Moon and Earth' by Robin Heath, published by Wooden Books 1999 and Amazon (spit,spit) seem to have quite a few copies for sale here https://www.amazon.co.uk/Sun-Moon-Earth-Wooden-Books/dp/0802713815 Less than 60 pages but with lots of the simplest of diagrams you will ever find in a book. A real treasure.
Must remember to return my copy to Cerrig sometime …. err sorry, got to go, nature calls!
Posted 29-03-2021 at 23:17
ArchAstro, many thanks for the video and for giving new life to the thread as I'd missed it previously. I'm rather astronomically challenged and usually work with astronomical events as numbers whenever possible, but my work may end up asking more of me than that and all assistance and instructional material is greatly appreciated.
Orpbit thank you for your diagram and comments, I especially like the spirited remarks about "polymaths" and always marvel when others reach similar conclusions to my own, controversial as they must be.
You have a very interesting calculation there in that if I try to run the calculation with my usual suspects, I get a solar year of unusual accuracy that is usually unattainable because the only way I know to generate it is excessive exponential division of the Megalithic Foot that I use by 12, but it thus also takes an excessive amount of 12^n to recover it, so it's generally proven unretrievable and therefore inconsequential.
It hadn't occurred to me yet that it might not be beyond the reach of the consensus mean circumference since that itself is generated by exponential use of 12^n (12^5 = 24883.2 / 10). I think it might be said safely enough that such a number is therefore already more than halfway to recovering the elusive, more accurate solar year value (1.177245771 / (12^8) = (1 / (365.2437805)) / 10^n
I've no idea what the outcome might be of pursuing it further, but that is certainly a very interesting possibility that must be work looking into more.
Posted 07-04-2021 at 19:43
One other view to show how the changing orientation of the lunar orbit over the 18.6 year cycle (orbital precession) drives the maximum and minimum standstill positions:
[ This message was edited by: ArchAstro on 2021-04-07 19:45 ]
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Posted 30-10-2020 at 19:17 
but any advances on this very welcome:
