Sky and Telescope - November 2017 - 32

Mystery Solved?

ing which time it kept the same light, and he then lost sight
of it by going in the house."
Maskelyne then tried to verify the time, which Lady Booth
felt was later than six o'clock (around sunset). He met with
a Thomas Stretton, who had also come forward. They went
to where Stretton had stood in St. John's Square, London,
and Maskelyne had him point out where he had seen the
Moon "with respect to the opposite house and chimnies over
which she appeared." Not the Astronomer Royal for nothing,
Maskelyne describes how "with the help of a pocket compass
and small wooden quadrant, I found the bearing of the place
in the sky . . . to be 80° west of the magnetic south, or 56°
west of the true south meridian, and the altitude 34°. Taking
the moon's right ascension from the nautical almanac for
the 7th of March . . . with the bearing abovementioned, and
the latitude of St. John's Square taken 51° 31′," he calculated
that the observation must have been made not far from eight
o'clock, "and therefore the two observations agree as nearly
together as can be expected."

Stretton must have pointed with remarkable accuracy, and
Maskelyne's pocket compass must have been a good one too.
Just a 14° pointing error could result in an hour's time error.
But Maskelyne was making the most of this opportunity.

Star of the Show?
Suspiciously, an occultation of 1st-magnitude Aldebaran had
begun about an hour earlier and ended a half hour earlier.
The occultation was a near-grazing one. For Norfolk, as we
can calculate quite precisely from our vantage in the 21st
century, the star disappeared on the Moon's dark limb at 6:57
p.m. local mean time and reappeared from behind the bright
limb at 7:33 p.m. LMT. (If Norwich was still using the older
system of local apparent solar time, its clocks would have read
11 minutes earlier.) A half hour after the occultation ended,
Aldebaran would have been plainly visible about half a lunar
diameter to the Moon's right, off the bright limb.
But one hour earlier, Aldebaran was slowly skimming along
the Moon's dark limb - at just the correct orientation of the

Wilkins's Star in Your English Class
» We have no busts or portraits of the observant Wilkins,
and in 2013 his lighthouse at Orfordness (below right)
was abandoned to the encroaching sea. But his star may
be memorialized forever in Samuel Taylor Coleridge's
The Rime of the Ancient Mariner:
The stars were dim, and thick the night,
The steersman's face by his lamp gleamed white;
From the sails the dew did drip-
Till clomb above the eastern bar
The hornèd Moon, with one bright star

And with that evil omen, the ship's crew give the albatrossslaying Mariner a dirty look and drop dead, supernaturally.
Coleridge wrote the Ancient Mariner in 1797-98, just
three or four years after the publication of Wilkins's sighting
and Maskelyne's analysis. Coleridge was almost surely
aware of these; he was an avid reader and devoured
articles about every kind of natural curiosity. Maskelyne's
report in the Philosophical Transactions created a stir,
prompting a lengthy summary of the sighting in the more
popular British Critic - which was, like the Phil. Trans.
itself, one of Coleridge's regular reads.
u SPOOKED Samuel Taylor Coleridge's Rime of the Ancient
Mariner went through countless editions in the 19th century; a
particularly sumptuous one was illustrated by Gustave Doré.
Bottom: Wilkins's recently abandoned lighthouse.

N O V E M B E R 2 0 17 * S K Y & T E L E S C O P E

ENG R AVING: GUSTAV E DORÉ. LIG H THOUSE: JOHN FIELDING

Within the nether tip.

Sky and Telescope - November 2017

Table of Contents for the Digital Edition of Sky and Telescope - November 2017