Sky and Telescope - October 2018 - 37

Disentangling Controversies
Almost immediately, complaints arose about poor imaging.
Finger-pointing letters sailed between the Northern and
Southern Hemispheres, some printed in British newspapers.
The Southern Telescope Committee and the Grubbs had made
what in retrospect was a problematic call. Instead of sending
Howard south with the telescope to supervise its installation,
the intended primary observer - a Cambridge mathematician
named Albert Le Sueur - was hired by the Melbourne Observatory. Le Sueur was sent to the Grubb factory to witness the
casting of the mirrors and other key milestones, and to learn
how to reassemble and operate the telescope, as well as the
mirror grinding and polishing machine. But once en route to
Australia, Le Sueur was on his own and had to make judgment calls. Grubb had speciﬁed that the mirrors' protective
coating of shellac be removed with pure ethyl or methyl alcohol. But pure alcohol was in short supply in Victoria. Instead,
Le Sueur started the job using methylated spirits and ﬁnished
with pure alcohol. Although the smaller mirrors retained
their high polish, either the shellac applied to one of the
primary mirrors in Dublin or parts of its surface may have
been contaminated. A cloudy residue yielded diffuse reﬂections, and accusations ﬂew. Making matters worse, an irate
Melbourne amateur astronomer wrote angry letters both to
British and Australian scientiﬁc societies, claiming (inaccurately) that "[t]he instrument has cost us colonials £14,000"
and asserting, "It is a grievous failure."
Over the next year, Le Sueur hand-polished both primaries
with washed chalk to near perfection, but in August 1870 he
resigned in frustration and returned to England. Although
he and Melbourne Observatory director Robert Ellery were
staunchly backed by the observatory's capable Board of Visitors, the bad-PR mud stuck.

p OBSERVATORY OVERVIEW This image offers a view of the Melbourne Observatory as it appeared in the 1880s. The main observatory
building is at center. The GMT, workshop, and engine for the mirrorgrinding apparatus are at the far right.

In the meantime, no one in the Southern Hemisphere had
experience in working with a telescope of such a large aperture, so on nights of ordinary seeing, a person accustomed to
observing with smaller apertures could ﬁnd the GMT's performance on a planet or double star actually "disappointing,"
noted Ellery. But "on really good nights it is quite different . . .
indicating an optical perfection which under other conditions was not apparent."
Moreover, the Southern Telescope Committee's intended
observing program - visual observations of nebulae to detect
changes - was highly subjective, depending on individual
observers' visual acuity and artistic skill. Indeed, for those
nebulae that were distant galaxies, detecting any change
(short of an extragalactic supernova) over mere decades
was downright impossible - although, of course, absence of
change was a crucial test.
Finally, after the ﬁnancial crash of the 1890s nearly halved
the observatory's budget at a time when it had committed
heavy resources to the international Astrographic Catalogue,
the GMT was not adequately maintained and most of the
astronomers' meticulous drawings were never published.
Against this background of woes, in 1904 Ritchey parenthetically commented in a treatise on making and testing
t PHOTO ASSIST Since no original drawings for the GMT survive,
photographs such as this one, which shows the telescope as it was in
1875, have been crucial in helping the restoration team reverse-engineer
the telescope's assembly. The weight hanging next to the man (who is
believed to be Joseph Turner) and the chain going over the top of the
larger pier were part of Thomas Grubb's design to relieve frictional load
on the main bearing of both axes so the telescope could be clock-driven.
The clock drive is next to the weight.
sk yandtelescope.com * OCTOBE R 2 018

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Sky and Telescope - October 2018

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