VIEWS
Sir Arthur C Clarke
Mark E Bailey
Asking about Antikythera
Imaginary
creatures
I was very interested in your
December 2000 issue as I have been
fascinated by the Antikythera
Mechanism for many decades. In
fact, I was responsible for Derrick
Price’s Scientific American article
on the subject, as it was I who
introduced him to the editor.
In 1965, at the International
Astronautical Federation’s Congress, I made a point of visiting the
Athens Museum and asking to see
the Mechanism. With some difficulty it was discovered in a basement,
in an old cigar box. No-one seemed
to realize its importance!
I hope that situation has now
been rectified.
Sir Arthur C Clarke, ‘Leslie’s House’,
25 Barnes Place, Colombo 7,
Sri Lanka.
David Wright
The turn of the screw: William Gascoigne’s micrometer
I am writing to ask for assistance
from A&G’s readers. The distinguished double-star observer Paul
Couteau has stated that the filar
micrometer “goes back to Auzout”.
True, Auzout (1622–91) did develop the instrument in 1667, but the
Englishman William Gascoigne
(1612?–44) produced one nearly 30
years earlier, in 1639.
Gascoigne’s micrometer appeared
in the same year that Gérard Désargues issued a book of modern geometry studying triangles in perspective, Jeremiah Horrocks observed
the transit of Venus and Pascal laid
down the foundations of modern
analytical geometry. Gascoigne was
“intensely interested in accurate
results”. He fixed telescopes to his
measuring instruments and clearly
had a gift for invention. Sadly, he
was to die at the Battle of Marston
Moor on 2 July 1644 while fighting
on the side of the King against the
forces of Parliament.
Gascoigne was a country gentleman of Middleton, near Leeds. In
1638 he had managed to fit a
marker point in a telescopic field of
view. He took the innovation further by introducing a second marker. As Allen Chapman has commented: “One marker could remain
fixed, and the other could be made
to move under the control of a finepitched screw. By knowing the full
angle encompassed by the telescope’s field of view, the observer
could enclose an astronomical
body, such as the Moon, between
the fixed and moveable pointers.
They could then use the turns of
the screw controlling the moving
pointer to work out the fraction of
the field enclosed by both pointers
and thereby measure the Moon’s
angular diameter with unparalleled
accuracy.”
Robert Hooke (1635–1703)
demonstrated this invention to the
Royal Society at the later date of
1667. The eminent amateur
astronomer, the Rev. T E R Phillips
wrote, “of the various forms of
micrometer used for the measurement of small quantities in astronomical observation, that known as
the filar micrometer is the one most
generally employed”. Indeed, this
class of instrument reached its engineering zenith in the 19th century.
Makers such as Troughton &
Simms produced fine examples, as
the writer can confirm from practical experience.
Does any reader know more
about Gascoigne’s instrument and
how he used it?
David Wright, Caterham, Surrey.
References
Phillips T E R and Steavenson W H
(eds) 1923 Hutchinson’s Splendour of
the Heavens vol. 2 London, Hutchinson
& Co 950.
Simms W 1852 The Achromatic Telescope London 56–62.
Couteau P 1982 Observing Visual Double Stars trans. W H Batten, MIT Press
48.
Chapman A 1994 Jeremiah Horrocks
and Much Hoole 9.
Ronan C A 1967 Their Majesties’
Astronomers Bodley Head 50.
Woolrych A 1965 Battles of the English
Civil War Pan Books.
Following the article by H J P
Arnold (A&G 42 1.10), readers
may be interested in more Moon
Fun at www.arm.ac.uk/moon_fun
.html. This shows both the “kicking
donkey” and “President Kennedy”
(or Elvis, or possibly some less celebrated figure). The recent book by
E A Whitaker (Mapping and Naming the Moon, CUP 1999) has an
interesting historical discussion of
other shapes, animals and faces that
have been noticed on the Moon.
Mark E Bailey, Armagh Observatory.
H J P Arnold
Bark at the Moon
Mistaken identity
The Editor extends apologies to Hazel
McGee, whose excellent photographs
illustrated the report of the Pro–Am
Astronomy discussion meeting in the last
issue (A&G 42 1.31–1.32). It is always a
pleasure to be able to show the human
faces behind the research we publish, but
in this case we omitted to credit the
photographer. This is our mistake and
not the fault of the author, Margaret
Penston, nor of the photographer.
Right: Attendees of the RAS Pro–Am
meeting of 16 September 2000 assemble
in front of the University of London
Observatory, Mill Hill. (Pic. Hazel McGee.)
The Sun is not to be outshone by the
Moon when it comes to phenomena
exercising the pattern-recognition
capabilities of the human brain.
Here is an image exposed through a
DayStar hydrogen alpha filter. The
seeing was not good at the time and
the resulting lack of fine detail contributed significantly to a cluster of
Sun spots appearing very much like
– the face of a dog.
H J P Arnold.
April 2001 Vol 42
2.9