In 2006 a major declination standstill limit of the moon will happen
(happens every 18.61 years) and this web page will report on the
of this event around the world. The following ideas/questions will be
Many locations in the world, where lunar standstill limit
could have occurred in former times, will be studied. At this moment
following locations will be covered:
If you want to do things at the same or other locations, let me
Be aware that the difference between major (declination)
and major azimuth standstill limit can be a
of tropical months. Different locations on earth can also have
sequences of major azimuth standstill dates (due to the fast moving
along its orbit).
Most lunar phases around the major azimuth standstill limit are between
20 to 70%, as know by theory that
moons are close to a major standstill limit.
Can the above mentioned lunar phases be
under all circumstances (day/night time and low apparent altitudes),
how could they be utilized in former times? If possible a theoretical
would be nice (like an extension of visibility
if not possible than pragmatic rules of thumb would be a welcome
Investigate if rise, set, meridian transit, reappearing or other
at the locations.
Determine the influence of actual (and changeable) astronomical
refraction on the sequence of the event dates (accurate measurement
equipment needed like theodolite).
Get an idea how the events would have been experienced in
former times (say 3000 BCE), also taking in account the change of
Determine the best way to predict, calculate and record the
Important: There is a difference in
major/minor standstill limits in declination (which is the definition
major standstill limit) and the definition I am using below, which is
major/minor azimuth standstill limit. This is because the rise/set
of the moon do not necessarily have to be the same moments as reaching
the extreme declination. The same phenomena will change dates due to
observation location. See this link
for more info.
As already studied earlier,
the date of the real major azimuth standstills limit is not
From that study, the window of 0.4° is there due to the fluctuation
of the azimuth value of the major azimuth standstill limit over a long
period (many cycles).
Furthermore the astronomical
will change the azimuth of set/rise point. Between winter (1030 mbar,
and summer (990 mbar, 20°C) the difference in refraction can be
(which is a small estimation; in real practice it can be larger, up
to 30% of the nominal value) in apparent altitude. This is
0.3° change in azimuth.
So all in all it is very difficult to determine the date of the real
major azimuth standstill limit using a megalithic building.
Another way of looking at it, is looking at the calculated azimuth
different dates and different locations for months around the
major azimuth standstill limit date. This was done for Maeshowe
(Orkney, Scotland), Callanish I (Lewis,
Scotland), Mound A, Boyne Valley
(Ireland, latitude: 53o 42' N and longitude 6o
29' W, height 30 [m]), Knocknarea
(Ireland), Chimney Rock (USA, longitude: 107°.3115 W, latitude:
N, height: 2.25 [km]) and Point Lookout (Australia, longitude:
E, latitude: 27°.426 S, height: 0.01 [km])
In appendix II the major
azimuth standstill values
are determined in the period 2005-2007 for the above mentioned
(the form of the moon has not been evaluated
in this appendix). The major azimuth standstill limits found, change
per location and rise/set event:
southern major azimuth standstill limits:
Sept. 29th, 2006 (Maeshowe set, Callanish I set,
Mound A, Boyne Valley
Sept. 2nd, 2006 (Maeshowe rise, Callanish I rise,
rise). An azimuth difference with Sept. 29th, 2006 of
max. 0.07° (this could be due to the linear interpolation).
northern major azimuth standstill limits:
April 4th, 2006 (Maeshowe set+rise, Callanish I
set+rise, Mound A, Boyne Valley
set+rise, Knocknarea set+rise)
In appendix IV are the major
standstill for 2007 given (they are of course not so extreme as the one
in 2006, but some people still might find it interesting to investigate
on these dates)
Conclusions on azimuth standstills
Comparing results for 2005-2007 period
So the real southern major
standstill limit happens on Sept. 29th, 2006 and the
major azimuth standstill limit on April 4th, 2006. But from
the above one can also deduct that other dates are very close (at least
using JPL and linear interpolation). If we take into account the
window of astronomical refraction, we have at least 4 to 5 dates in
azimuth range (these entail a period of ~1 year, with intervals between
the dates of multiples of the lunar tropical
(average ~27.32 days).
This idea is also mentioned by Thom (,
"The Moon, it is true, in no sense stands still, but for about a
year the limiting declinations do not vary more than 20 arc minutes, so
that for month after month the Moon's declination goes through almost
The dates when the maximum and minimum meridian transits happen are
from the azimuth and declination standstill events, see Appendix
The phase periods (each period is almost 7 days in length) used in the
below text are as follows (pictures of the moon are at meridian transit
and come from NASA
start new-ish moon (0%)
end of new-ish and start quarter-ish moon (25%)
end quarter-ish and start of full-ish moon (75%)
end full-ish moon (100%)
The distribution of phases near the northern azimuth for example
I can be seen below (azimuth calculated is of centre of the moon, for
positions see here):
If we only take the moons in full darkness, astronomical and
twilight and we take into account that the azimuth of the upper
part of illumination watched is different for lunar phases
we get the following picture:
In both cases: quarter-ish moons happen closer to the northern azimuth,
followed by new-ish moons and then full-ish moons.
The major azimuth standstill limit though becomes 335.6° instead
of 336.1° and the difference between new-ish moons and full-ish
is some 0.6°. Remember this is only an example, other locations can
have different values and sequences.
If one takes the 15 most northern quarter-ish moons and the 15 most
full-ish moons one gets the below distribution irregardless of
twilight/darkness conditions and azimuth calculated for centre
the moon (for other positions see here):
This could provide an idea how alignments will be distributed when
looking at full-ish moons and quarterish moon (which spans a period of
2.5 years), so this include ritual aspect (full-ish moon) and the proto-scientific
aspect (quarter-ish moons), for the 2005-2007 time frame (at Callanish
This gives an average of 334.7° +/- 0.7° (1s),
while the major azimuth standstill limit is 336.1°. So a differance
of around 1.5°.
The total error in lunar azimuth (near standstill limit and close to
Callanish I), is a combination of:
uncertainty of which event is recorded by the monument (so
quarter-ish moons): 1s=0.7°
uncertainty if the lower limb, center or upper limb of moon was
uncertainty about the astronomical refraction: 1s=0.3°
uncertainty about the value of the standstill limit when looking
periods of 18.61 years: 1s=0.1°
So when measuring the average alignments of a lot of monuments, assumed
to be directed to azimuth standstill limit, a resulting error of around
0.9° would be expected to be seen.
Favored moon set/rise event at minor/major
The below text is copied from North ,
Fig. 209. Extreme values on the graph of the Moon's
declination for a typical series of lunations around major northern and southern standstills. The
period covered is about 43 months. The lunations are numbered consecutively and the approximate phase
of the Moon is shown for each.
The new moon is strictly unobservable, lost as it is in the glare
of the Sun. Although the Moon becomes visible within a day or two of
moon, the general insignificance of corresponding declinations (and
azimuths) when it does so is noteworthy (see the points marked 6, 21,
25, 34, 36). Although Semitic peoples have attached great religious
to the first observation of the lunar crescent after the new moon, they
have taken no particular notice, as far as can be seen, of lunar
standstills. The quarters give more or less the true extremes. At first quarter
(the disc is shown blackened on the left half) the Moon has passed the
Sun in ecliptic longitude by about 90°, so the Sun is high in the
when the Moon rises, but has set long before the Moon sets. Only under
very special atmospheric conditions is this moonrise visible. At third
quarter, it is only the rising of the Moon that is likely to be visible. Full moon is a conspicuous event, notable in its own right, and
observations of its occurrence on the horizon could have been observed
if they fitted readily into the scheme of standstills. Consider the
roughly speaking, if the Moon is on the horizon at full, then the Sun
be far from the opposite horizon. As far as visibility is concerned,
and parallax are of much less importance than the difference in
of the Sun and Moon. In cases 7 and 37, at the winter solstice, the
is to the north of the ecliptic degree opposite the Sun, so that when
Moon is on the horizon, whether rising or setting, the Sun is a few
above the opposite horizon. In both cases the Moon is difficult to see.
In cases like 22, however, with the Moon south of the ecliptic, it sets
before the Sun rises, and rises after sunset. This describes the ideal situation, but winter full moons like 7
and 37 should not be dismissed too readily. The Moon moves
thirteen degrees per day—and a day on either side of full moon makes
difference to its declination, but through change in ecliptic longitude
can make all the difference between visibility and invisibility. First,
therefore, some remarks from the devil's (or rather skeptic's) advocate. Even alignments to cases like 5, 9, 35, 39, 20, and 24, while
major standstills nor full moons, might have been recorded. There are
causes of uncertainty in the smaller details of interpretation of lunar
alignments. To take two of a dozen potentially problematic instances:
after an azimuth has been converted to a declination, only a
of an obliquity and a lunar inclination has effectively been found.
the obliquity is known independently (say from the year) no conclusion
can be drawn about the inclination, and thus none about its difference
from the mean. Secondly, the same alignment might be ambiguous, for
as between the direction of (1) an actual extreme of type 7, and (2)
only visible Moon in the neighborhood of an extreme of type 15
that the weather interfered with other observations). It seems reasonable to suppose that observations were made over
periods of time long enough to stake out correctly alignments to
standstills. As for major standstills at the winter solstice full moon,
they could have been observed wherever an artificial horizon was
high enough to ensure that the Sun had well and truly set by the time
Moon rose. It might have been twilight still, but the Moon would have
visible, given the right atmospheric conditions. Which types of lunar alignment are then most likely to have been
favored? For reasons that have now been explained, the following three
seem most probable:
Northern lunar setting at first quarter, being more or less
major standstill. Occurring near spring equinox (see case 15).
(i) is increased over its mean value by 8.7' (...). In this
it is intriguing to recall Pliny's reference to the culling of
by the druids on the sixth day of the moon.
Southern lunar rising at third quarter, being true major
Two weeks later than the above, near the spring equinox (see case 16).
Inclination as above, but declination now negative (south of equator).
Southern lunar rising or setting at summer full moon. The
at this type of major standstill is then a minimum (10.0' below the
but the assumption is that the brightness and general character of full
moon makes it an attractive proposition.
The example of Stonehenge, however, recommends a fourth bullet:
Northern lunar rising or setting at winter full moon. The
is that under bullet 3. Given a regular horizon such will occur
with the Sun above the horizon, but sunset may be guaranteed either by
an artificial horizon or an unusually high lunar horizon.These suggestions do not preclude alternatives (such as phases near
full moon, or cases where the best that can be found over a short
is for a nondescript phase), but the bullets listed here do
inherently more probable than the rest. There remains the problem of how the perturbation affects minor
standstills. From similar arguments to those given already,
spring settings and third-quarter autumn risings seem intrinsically
to have attracted attention (as being near the absolute limit), as do
full moons (on account of their appearance and brightness). Adjustments
to the inclination are exactly as in the corresponding bullets
for major standstills, and the corrections in azimuth are of the same
A point about observing quarter-ish moons in Ponting (,
page70-71): At these phases the moon has no illuminated upper limb (or
lower limb). A little bit lower (at least within 0.125 degrees
the moon is of course illuminated. Ponting says that this will not be a
valid moon form to observe! I think Ponting assumes that the neolithic
people knew the moon was round and because the upper limb existed but
they dismissed that form. I think that neolithic people perhaps did not
(yet) know that the moon was round, but perhaps they thought it to be a
form that rotated in the sky (I think one could design such a form
easily that looks like the moon when using naked-eye observations, by
So I would say that with a quarter-ish moon, the upper part of the
illuminated moon form can be used for observations, see
Curtis has publish a document on
Callanish major standstill limit event [Curtis ). Two things are very interesting
in this document:
it gives a graph of the
apparent altitude for each limit event, so including a day before
and after it. This helps you plan a trip to Callanish!
It gives a nice overview of which lunar phase happens during the
limit events over the seasons. This has
Thom did observations at monuments and documented the declinations
(necessary when comparing multiple locations). See below picture from
(, page 77):
Thom does not talk about different lunar shapes at different monuments.
So looking at the graph it seems he is working from the idea that full
moons are observed (semi diameter is always 15'.9). But the
things is that these full moons are not at the major
quarter moon are!
This thus needs more study why Thom did not mention this. This could be
due to the fact that Thom used a
wrong formula and because of that he thought that full-ish (and
new-ish) moons were at the extremes (and not the quarter-ish moons).
extrapolation methodology proposed by Thom could perhaps overcome this
page 83). Ideas are
The following pages which are interesting (if one is member of the archaeocosmology
group one can see the below links):
A good list of criteria is given by Schaefer
 concerning alignments (so
intentional). Purple statements
added by author of this web page. Intentional can be by design or by
usage of the monument. The
below criteria can also be used by any other science (like
the astronomical case for the
claimed alignments (Schaefer
had this criteria as the last criteria in the list)
statistical significance over the null hypothesis, where a
multi-site analysis is almost essential (a single site will never be
able to reach a pure statistical significance). Schaefer  assumes that minimually a 3 or
4-sigma threshold is needed.
There can be chosen a few null hypothesis like:
random direction between 0° and 360° (so real null
random direction between 0° and 180° or 180° and
azimuth of random Sun rise and/or set
azimuth of random Moon rise and/or set
historical documents or ethnographic information on the culture
in question or more weakly, ethnographic analogy with other cultures.
For an analogy, the argument might go something like "Almost all
recognize the solstices while many have alignments to them, so it is
plausible to think that a solsticial orientation observed for a
prehistoric monument like Stonehenge is actually an alignment."
Bradley's conclusion on lunar alignments is: "This conclusion places a heavy
burden on anyone who claims that a lunar orientation is actually an
alignment, as they must provide evidence of intention when all evidence
shows that no one has any interest at all."
Literature on visibility
According to North, Ponting,
Curtis and some other people, it is in principle
possible to see the set or
rise of a moon's form from say 25% illumination at low apparent horizon
altitudes (thought not during day time).
It is planned to change the visibility
(based on Schaefer ) in such a
that it can also predict the visibility of the
in the sky (and not only in an enclosure).
The below table of lunar phases which happen in general at (near)
majorstandstill events has been compiled using the information from
(, page70-71), North,
others and myself. It also provides ideas about the visibility the set
and rise events.
Major standstill (a)
Near solar event
Red cells are most
moments favored by North Why are blue cells not
ranked by North? I would rank them also. Green cells are less
likely, but still possible, I think.
Partly lit moon
If looking at the effect of the different forms of the Moon (using SkyMap
to determine the orientation of the form) and the experienced maximum
set or rise moments with upper part of illumination watched:
With full-ish Moon set and rise, the upper limb is at 0.25°
center of the Moon.
For third/rising (first/setting) quarter-ish Moon (25-75%), the
of illumination watched could be minimally 0.125° above the center
of the Moon. So the rising (setting) azimuth could be max. 0.5°
(less) at Callanish I.
Rise paths of third-quarter and full moon each at their min. major azimuth standstill
In this case an alignment would differ if one is looking at first
seen or the invisible upper limb of the Moon at quarter-ish
This changes the distribution of phases and azimuths.
set or rise moments with bottom part of illumination watched:
With full-ish Moon set and rise, the lower limb is at 0.25°
center of the Moon.
For third/rising (first/setting) quarter-ish Moon (25-75%), the
part of illumination watched is 0.25° below the center of the Moon.
So not different from full-ish Moons.
meridian transit moments:
For all forms (25-100%) the upper (or bottom) limb are at 0.25°
above (or below) the center of the Moon
Any part of the Moon could be reappearing, so there is no real
looking at any form of the Moon here.
using formula (12), (10), (9) and (11) to determine
just the moon
(Bmoon) seen on earth. Done for apparent altitude of 1°, 0.75°
using formula (35) (with Bsource=B+Bmoon)
or (36c) (with z=0.2°) to
(by iteration) which B just reveals the setting or rising moon.
using the table
in Schlyter, horizon brightness at different twilight conditions is
The below graph is the result (with the following important parameters;
visibility range 20 km, location Ireland, height 60m, around May, 23
Rule of thumb
Although the variability of the atmosphere makes it hard to predict
will be visible, one could imagine good days hopefully were more
in former times;-). At this moment I don't have yet a final rule of
but based on some 40 observation to
hazy horizons near sea-side here in Ireland and with apparent altitudes
new-ish moon (say 5-25%) are visible at rise and set when it is
than nautical twilight.
An 1.7% moon was visible at 0.8° apparent altitude at nautical
quarter-ish moon (25-75%) can be seen rising and setting
than cival twilight
full-ish moons (75-100%) can be seen setting and rising when
This rule of thumb will be updated when more information is gained.
rule of thumb is mapping the theoretical model.
Several reasons can be heard for why and when to witness a celestial
when real full moon
when full-ish moon
when quarter-ish moon
when maximum (geocentric) declination
when azimuth or altitude are maximum or minimum
at set, rise and/or transit times
at northern and/or southern standstill events
when greatest possibility of good weather
at a certain location and horizon profile
when in (holiday) break
when a trip is organized
for scientific of ceremonial use
due to a certain ideology/religion/etc.
it is mystical/logical that neolithic might be interested in such
fits into the frame of mind of a person<>
If people have additional reasons to celebrate an lunar/solar
The above reasons are all valid. The above reasons are used at
present, so I am sure that all these reasons (and more) were also
used in pre-historic times (and thus perhaps fixed in a neolithic
Any reason is a valid intend/experience, because the reason can be the
driver for human action (even if it is scientifically not correct).
Azimuth value of major azimuth standstill
in ~3000 BCE
The azimuths values of major azimuth standstill events in ~3000
different value than at present (~2000 CE)
due to change in obliquity. For the Callanish I location this has an
influence on the azimuth, which has an influence of some 0.6° on
Major azimuth standstill dates until 2100
The following major azimuth standstill events are calculated for
around the major standstill limit and for the location of Callanish
(the form of the moon has not been evaluated
in this appendix):
One can make one's own overview of set/rise dates of
the moon near their major/minor standstill limit. A web-page show how
to get the JPL data.
If one follows the above given method (don't forget to fill in the
longitude, latitude and height of the location you want to see), one
gets an e-mail back from JPL with all the set and rise times.
Save and rename the e-mail content to a file with extension .txt. Start
you spreadsheet program (like Excel) and get the text file in it using File -> Open... with File of type: Text files *.txt and
use Delimited option with Comma delimiters and Finish for opening the file. When
the file is in the spreadsheet, select the whole worksheet and then Data -> Sort... on the Column D (Azi_ column).
This results in an ordered file, where one can see which dates are the
I would like to thank the following people for their help and
feedback: Margaret and Ronald Curtis, David McNaughton, Thomas Schmidt
and all other unmentioned
Any remaining errors in methodology or results are my responsibility of
course!!! If you want to provide constructive feedback, let me