VMs: The Star Chart on f68r3

["Robert Teague" <rteague@xxxxxxxxxxxxx>]

My main hobbies are astronomy and astrophysics, so naturally
I find those folios in the VMs to be the most interesting.

This past Sunday I decided to investigate f68r3, since it has
a star group recognizable as the Pleiades cluster in Taurus.
I used the planetarium program Starry Night Pro for this research.

I turned off all sky objects except stars and planets, turned
on the constellation boundaries, made sure star magnitudes
were limited to brighter than +6 (the limit of naked-eye
visibility), and randomly chose a spot in Europe to observe
from (Lat 50N, Lon 10E).

The Pleiades are carefully drawn, and using their orientation,
found matches for all the stars shown. The diagram shows
an area about 15° in diameter.

The star with the Pleiades in the northwest segment is not
Aldebaran, as has been guessed, but a 5th magnitude star
identified as HIP 17954. In the northeast segment, the star
closest to the Moon is 63 Arietis (Aries), and the other is
Tau Arietis. In the southeast segment, closest to the Moon
is Lambda Tauri, with 30 Tauri upper, and HIP 18805
lower.  Due to the proximity of the Hyades, identifying
the stars in the southwest segment was tougher, but I
finally settled on 43 Tauri (closest to the Moon), Omega
Tauri (next closest), Kappa Tauri (bottom left) and
Epsilon Tauri (bottom right).

Setting the sky in motion, I observed that the Moon, Sun,
and planets traverse the area bracketed by the identified
stars. The object in the center of the diagram is clearly the
Moon, and I therefore concentrated on it. The Moon's
path on the diagram is right to left, across the artistic star
segments.

As years passed, I observed that the path of the Moon slowly
moved northward until it occulted the Pleiades, then headed
southwards again. This took place over a period of some
twenty-odd years. The "S" curve connecting the Moon and
the Pleiades does not mean occultation, as the position of
the Moon as shown is near the southernmost part of its path.

Based on the orientation, the Moon is shown in a waning
gibbous phase. Satisfying that condition, and to be in the
position indicated by the surrounding stars, happens only
in mid to late October of the year. I further imposed the
conditions that it is a nighttime event, and that no other
object would be within the 15° circle.

Setting the year to 1200 AD, I let time go forward and
observed the results. The first date I found that satisfied
all the conditions was 8 PM on 20 October 1233 AD.

I will continue to observe and record later dates up to
the 16th century, and report the results.

I remember reading in the list archives that somebody else
has planetarium software. If they are so inclined, I ask that
they check my results. Any questions, reach me at
rteague@xxxxxxxxxxxxx , and thanks.

Robert

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