Sky and Telescope - March 2016 - 37

Retired scientist Klaus Brasch is a docent at Lowell Observatory. Ralph Nye is Director of Technical Services.

BEFORE AND AFTER The team performed ﬁne-scale restoration work
throughout. Here, the hollow declination shaft (coming down from top)
ends inside the endcap at bottom; the counterweight shaft extends on
below. Inside the declination shaft are two coaxial rods that control the
right-ascension slow motion and its clutch. They end at the two ﬂat gears
seen above in the endcap, here stripped of its outer parts. Other gears
engage those to turn the right-ascension sector arm (the large V-shaped
part at top) for slow-motion control, and to lock and unlock it.

RESTORATION TEAM From left: Peter
Rosenthal (mechanical), Dave Shuck (landscaping and dome), Glenn Hill (woodwork
and painting), Ralph Nye (project manager
and mechanical), and Jeﬀ Gehring (machinist
and mechanical). The project took 20 months.

LOWELL OBSERVATORY (3)

By far the most delicate and precious components
of this classic telescope were the irreplaceable 12- and
24-inch Clark objective lenses. The fronts of both
objectives were covered with years of dust, pine pollen,
and contaminants, but were otherwise unharmed. We
took both cell assemblies apart with great care, marking the positions of all components carefully on the
lens edges and cells as we found them. Original "V"
marks remained on the edges of both the crown- and
ﬂint-glass elements and lens cells, to show the intended
rotation of the elements with respect to each other, but
we reinstalled all components exactly as they were when
we took them apart - due to the unknown source of
the "V" markings (was a better matching of the lens elements done later?) and because the objective performed
perfectly as it was.
We cautiously cleaned the lens elements with Alconox
mixture, alcohol, distilled water, and Kimwipes. We used
a spherometer to document the radius of curvature of all
lens surfaces. We also recorded the thickness and diameter of each element and the spacing between them,
since no original Clark drawings or speciﬁcations exist.
All of the lens elements were uncoated, and we left them
that way for historical authenticity.
One unexpected ﬁnding was a soft, silver-colored
metal lining, most likely zinc, machined into both lens
cells at their contact areas with the glass. Another surprise inside the 24-inch tube was a special color-correcting assembly that had been installed to minimize chromatic aberration when the telescope was used during the
International Planetary Patrol Program in the 1960s.
Reassembling the mount and telescopes inside the
dome was far easier than their disassembly had been.
We polished and clear-coated all of the brass pieces and
most of the gearing, shafting, and other metal components, thereby highlighting for all to see the wonderful
1896 engineering and machine work that went into
construction of this historic masterpiece. In addition, we
fully restored to working condition one of the original
mechanical clock drives used to turn the telescope. This
beautiful, historic mechanism functions now as if it had
just been manufactured.
Lastly, we refurbished the observatory dome with
new, smoother-operating top shutters, extensive internal
and external wooden slat repair, and weatherprooﬁng
and repainting.
The ﬁve people involved with the restoration feel great
accomplishment and deep appreciation for the donors
who made this project possible. This storied astronomical facility now looks as if was built yesterday. It should
serve Lowell Observatory's public outreach program for
another 100 years. ✦

Sk yandTelescope.com March 2016

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Sky and Telescope - March 2016

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