After a year of intensive restoration work, Lowell Observatory’s Pluto Discovery Telescope is ready for its close-up.

Nearly every part of the 90-year-old instrument and accompanying dome has been refurbished, from the trio of 13-inch lenses to historic wooden shutters that open up to the stars.

With everything now complete, the telescope is working as well and is looking even better than it did when Clyde Tombaugh used the instrument to pick out distant Pluto 88 years ago, observatory staff said.

“It’s a beautiful telescope,” said Ralph Nye, part of the restoration team. “This is the way it should look.”

The public reopening of the Pluto Discovery Telescope is set for this Saturday.

Ralph Nye stands on an observing ladder behind the Pluto Discovery Telescope at Lowell Observatory. Over the past year, Nye led a group that completely restored the instrument and the building that houses it. Jake Bacon, Arizona Daily Sun

Work began early last year when a crane reached into the telescope’s white dome and lifted out a 7-foot, 350-pound tube, counterweights, and giant steel mount. Since then nearly every part of the telescope and the dome has been redone. The team removed, cleaned and reused everything down to nuts, bolts and screws — almost nothing needed to be replaced, said Peter Rosenthal, who also worked on the telescope.

The work also came in on time and met the project’s $155,000 budget with a few bucks to spare, Rosenthal and Nye said.

The thorough process was similar to what Lowell’s restoration team did on the Clark Telescope in 2014 and 2015. The Pluto Discovery Telescope itself needed less work, but the dome was in worse shape than the Clark’s, Nye said.

The team needed 40 tubes of caulking to seal up the exterior stone wall and they hand-brushed moisture-resistant coating on the rocks. The dome’s leaky tin siding required a new vapor barrier, and windows that were dry rotted and falling apart were replaced with custom glass and hardwood frames, Nye said.


Inside the structure, workers patched and repainted the dome’s stucco interior and restored the rotting wood shutters with panels that were custom cut, then stained and beat up a bit so they didn’t look too new, Nye said.

While the telescope’s lens system is of exceptional quality, everything else was kind of cobbled together and built in-house because the observatory was on a tight budget, Nye said.

When they ripped up the carpet, for example, they found tin can tops covering holes in the floor, he said. The carpet had so much dirt in it that they had to wear masks when they were carrying it out the door, he said.

Peter Rosenthal fits a large glass plateholder to the back of the newly renovated Pluto Discovery Telescope. The plates were used to take exposures of the sky. Jake Bacon, Arizona Daily Sun

The goal was function over form, Rosenthal said.

“I don’t think they cared about things (like looks) back then, they just wanted it to work,” he said.

Known as an astrographic camera, the telescope’s three lenses focus light onto a single glass photographic plate. Each image requires an exposure time of almost an hour, which would have been a chilly experience for Tombaugh on winter nights because the dome’s shutters have to be open to the sky, Rosenthal said. As a young observatory assistant, Tombaugh took the exposures, then scrutinized the glass negatives using a Zeiss blink comparator. On Feb. 18, 1930, he pinpointed Pluto — observatory founder Percival Lowell’s “Planet X.”

Now that restoration is complete, Nye is looking to put the Pluto Discovery Telescope back into use. He wants to be the first to use it to take color photographs. If they turn out well enough, he envisions enlarging the images and selling them in the bookstore, Nye said. Plus, a telescope that gets regular use will be better maintained than if it’s just sitting there “gathering dust,” he said.

Emery Cowan can be reached at (928) 556-2250 or