Sky & Telescope - August 2020 - 28

Telescope History

Early Instruments
In 1890 Saegmuller built his ﬁrst large refractor, for the
Catholic University of America in Washington, DC. The
9-inch objective was produced by local optician John Clacey,
who would subsequently make objectives for several Saegmuller telescopes. Clacey specialized in lenses with focal
ratios somewhat shorter than what was typical at the time.
This yielded a signiﬁcant advantage since a telescope ﬁtted
with a short-focus objective can ﬁt into a smaller dome, thus
reducing the overall cost of the observatory. The clock drive
for this instrument's mount sat in a windowed cube structure situated between the pier and the support for the right
ascension axis. This distinctive conﬁguration was common to
nearly all of Saegmuller's mounts.
The next three refractors that Saegmuller built utilized
12-inch objective lenses. One went to the Ladd Observatory at
Brown University in Providence, Rhode Island, the other two
to the U.S. Naval
Observatory and to
Georgetown University, both in Washington, DC.
All three telescopes featured
Saegmuller's patented "hand wheels"
for slewing in both
right ascension and
declination. Because
t DIALING IN THE
UNIVERSE Two defining characteristics of a
Saegmuller mount are
its star dials and hand
controls, both visible in
the author's 1986 photo
of the newly restored
Georgetown University
refractor.

AUGUST 2 02 0 * SK Y & TELESCOPE

t A FRIEND IN A HIGH PLACE While director of the Georgetown Observatory, Father
John Hagen helped acquire Saegmuller
telescopes for the facility as well as for Jesuit
colleges in the Netherlands and the Philippines. This photo was taken in 1914 when he
served as director of the Vatican Observatory.

electric motors were not yet available,
these controls were purely mechanical,
utilizing an innovative combination
of shafts and gears to link the hand
wheels to the axes of motion. One
particular challenge was the linkage
for the declination control, which had
to pass through the center of the right
ascension axis without being affected by its rotation. The hand
wheels made controlling the aim of the telescopes much easier.
Two conﬂicting anecdotes surround Clacey's role in the
Georgetown University instrument. The ﬁrst purports that
Clacey provided an f/13.5 lens because the Clarks declined to
make one with a focal ratio lower than f/15. This would have
been a problem, because the telescope was to be housed in
an existing dome that was too small to accommodate such a
long optical tube. The second story holds that originally the
Clarks supplied the objective, but it was found to be of poor
quality and so Clacey had to rework it.
Both the Naval Observatory and Georgetown instruments
featured innovative "star dials" (also called "ﬁnder circles")
that were mounted on the side of the pier and conveniently
displayed the right ascension and declination position of
the telescope. Although there's been some debate as to who
conceived the idea, the star dials wouldn't have been feasible
without the linkages that Saegmuller used for the mount's
hand wheels.

Going Big and Going Abroad
The two refractors that Saegmuller built next were also his
largest. He designed them for the Chamberlin Observatory in
Denver, Colorado, and the Manila Observatory in the Philippines. Saegmuller always considered the Chamberlin scope,
which employed a 20-inch Clark objective, to be a ﬁnancial
failure as payment came in the form of land in the Denver
area. Unfortunately, the lots awarded to Saegmuller lay in a
poor section of town, so even as their value didn't increase,
he had to pay taxes on them.
Work on the Georgetown instrument brought Saegmuller
into contact with Father John G. Hagen, director of the
university's observatory. Hagen played an important role in
acquiring Saegmuller refractors for other Jesuit observatories,
including the Manila Observatory's 19-inch refractor. Not
long after the telescope was installed, it survived the Battle
of Manila Bay in 1898, shortly after the outbreak of the
Spanish-American War.
Saegmuller next produced two refractors with 9-inch
objectives. Unlike his previous instruments, which had

G EORG E TOWN REFR ACTOR: TED R A FFERT Y; FATHER JOHN
HAGEN: COURTESY GEORGE TOWN UNIVERSIT Y LIBR ARY

Saegmuller took control of the company and began making large refractor
telescopes.
In my research, I inventoried a
total of nine Saegmuller refractors
with objective lenses 9 inches in
diameter or larger. Remarkably, eight
of these were built between 1890 and
1897 - a span of just eight years.
Since most large telescopes from this
era are referred to either by the observatory that housed them or by the
maker of the objective lens, my list
may not be complete. Regardless, I've
been able to verify that Saegmuller
indeed built all the instruments described in this article.

Sky & Telescope - August 2020

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