2006 was the year of the lunar standstill, the peak
of the wandering path of the Moon along the horizon.
I'm interested in the way the cycle is seen from
the Earth, and how it was used to align stones
with hills to form a sacred mandala.
My intention was to write a little programme , giving
an earth centred view point of the maximum and minimum
rising (and setting) points of the moon to show the
rising and setting of the moon at any time.
To do this, I've written a programme using the Swiss
Ephemeris astrological algoithms and thrown this
together over the Yule break. Feedback welcome, with
the usual disclaimers of user beware! I've tested
it on several Windows platforms, 98, 2000, XP and
it seems ok. Heres the link to download Moonrise
and Moonset calculator
Assuming you've managed
to download it ok, theres only one screen and this
is it. The top pane shows a styalised view of the
horizon, looking South. The tall vertical line is
due South, left and right are the East and West compass
points. North is behind. The calandar starts off at
the current date, read from your computer, with my
home location, Stroud, England Latitude 51 degrees
45 minutes (North) Longitude 2 degrees 12 minutes
West.
To change your location, click in the box and type
the numbers. Theres no error checking so dont be surprised
if odd things happen at the north pole!
Changing the date is easy,
by clicking on the calendar. Each time you change
the day or month or year, the plot of the moons rise
and setting is shown, with the moon phase too.
The other important bits of information shown are:
• Azimuth. As read from a compass, the number
of degrees from due north where the moon will rise
• Altitude. The highest point in the sky the
moon will reach, due south
• Moon Rise. The time of moon rise.
As you click on various dates the plot gets cluttered;
the buttons 'Clear' and 'Draw' do what they say, to
redraw the screen with the curent days plot.
Heres one of the interesting
points in time; the 11th June 2006 major standstill,
coincident with a full moon, and should be worth staying
up for. Here, the moons path on the horizon gets about
as far South as it can get, rising at 139 degrees
53 minutes and only reaching 10 degrees high in the
sky.
14 days later, through
the solstice on the 21st, she'll be rising higher
and higher each day, rising further north.
Note, all times are BST, and dont take summer time
into account.
For comparison, in 1997,
halfway through the 19 year cycle, the moon wanders
much less.
Accuracy.
Always a tricky one. The Swiss Ephemeris algorithm
is as good as you can get, and it takes into account
barometic pressure and temperature effects on the
rising and setting times, which will cause changes
due to refraction. I've used sea level altitude and
'standard' apparent conditions. The horizon is considered
to be at sea level. From the US
Naval Observatory the following note is given,
and their online calculator gives the same result
for moonrise. I'd love to see how it compares in real
life!
"Moonrise and Moonset conventionally refer to
the times when the upper edge of the disk of the Moon
is on the horizon, considered unobstructed relative
to the location of interest. Atmospheric conditions
are assumed to be average, and the location is in
a level region on the Earth's surface. "
Download
As usual, theres no waranty against it messing up
your computer, but I've done all the virus checks
and tried it on different Windows platforms, with
no problems. It can be uninstalled using the usual
'Control Panel / Add remove" tool, where it appears
as "Moon" Right click on the Moon below
and "Save Target As" the file Moon.zip to
a local temporary folder. Its about 3.8M Unzip and
run the Setup.exe file, and it will create a folder
in your c:\programe\ files directory called "Moon".
Just run the programme moon.exe, and you should see
the above! Alternatively, from the "Start"
"Programmes" menu at the bottom of the screen,
find "Moon"
Feedback appreciated! And
for more information on my calculator go to http://standstill.timholland.co.uk
timholland@f2s.com
