What's the Moon doing at Stonehenge

I take a lot of people to Stonehenge. I have a fairly good idea what the sun does in relation to the landscape and the stones. But the moon has been beyond me.  So I have been trying to work it out.



 draw
a little diagram with the sun over to the left, the earth over to the
right and put the moon orbiting the earth, with the new moon between the
earth and the sun and the full moon on the other side of the earth and
the half moons at right angles.

That really helps

Moonrise

The moon takes a month to go around the
Earth. At new moon the moon is near the Sun, and it therefore rises
at Sunrise and sets at Sunset but is not very visible because it is
near the sun.

At full moon by contrast the moon is on
the opposite side of the earth to the Sun – hence we see the entire
moon reflecting the sun light. Therefore the moon rises at sunset,
and sets at sunrise.

In between these times the moonrise
gradually changes.

So waxing crescent moon the moonrise is
2hours after sunrise, sets after the sunset

Half moon the moon rises in the late
afternoon and is up most of the night

Full moon rises at sunset and sets at
sunrise

waning gibbous moon Rises after
sunset, sets after sunrise

waning half moon rises at midnight,
sets at noon

waning crescent moon rises 2 hours
before sunrise, sets couple hour before sunset.

New moon – rises at sunrise sets at
sunset.

The lunar cycle does not divide neatly
into the sun cycle because 29 does not go into 365. Every 19 years
the cycles come back together because 19 years = 235 months. Meton of
Athens worked this out, the B Baylonians knew it, and they created a
metonic cycle of 19 years made up of 125 30 day months and 110 29 day
months.

I also read that the moon repeats
itself every 18.6 years. I'm not sure how these relate to each other.

Stonehenge is at the exact latitude
whereby the midsummer axis (NE-SW) hits the northernmost moonset and
southernmost monnrise(NW - SE)  at the major standstill (whatever that is) at a
right angle. This is marked by the 4 station stones.

Standstill is a phrase used by
Alexander Tom who invented the idea that Stonehenge is a astronomical
computer. It simple means the same thing as a solstice, the extreme
point whereby the moon begins to got back the other way

So at the summer solstice the line that
points to it through the middle of Stonehenge (NE-SW)  is a rightangles to the
lines that go through the station stones pointing to the extreme
northern moonset and the extreme southern moonrise (NW-SE). This isn't true at other latitudes apparently.

Also look at:

What's the Moon doing?