Amateur Astronomer Restores a Classic Historic Refractor

An old refractor telescope sees a second life under the night skies, thanks to the efforts of a dedicated amateur observer.

It’s always great to see classic telescopes back out under the night skies. We recently found out about a fascinating project to restore a century old refracting telescope. The project was undertaken by Valts Treibergs, a Minnesota Astronomical Society member. Valts is an engineer, telescope restorer, and long-time amateur astronomer.

We caught up with Valts recently, and he told Universe Today the fascinating story and background on the project:

“I have been restoring telescopes for quite a few years—primarily a number of Japanese refractors from the 1940s-1970s made by Goto, Royal Astro Optical Inc, Yamamoto, Unitron and others. In 2021, I found a dilapidated 4” refractor on Craigslist in Minneapolis, which turned out to be a nearly one hundred year old brass antique made by Brashear in Cleveland. This scope was cleaned up and I made a custom mount for it from scratch. In addition to the restoration projects, I also help maintain the fleet of loaner telescopes for the Minnesota Astronomical Society, for which I am an active member.”

Refurbishing Refractors

This may seem impressive, but soon, Valts came across an even more challenging project.

“Last November (2022), Ron Schmit (also a member of the MAS), approached me about an opportunity to take on some vintage equipment that has been in storage for decades at the University of Minnesota Institute of Astrophysics at John T. Tate Hall. I worked with professors Larry Rudnick and Evan Skillman to get access to these items – most of which were stored beneath the crawl-space of the rooftop observatory that houses the University of Minnesota’s Warner & Swasey 10.5” refractor used for public outreach events. Tate Hall was completely remodeled in 2018, so many items were scattered about and displaced.”

Soon, Valts came across one particular item of interest: a large, disused 6-inch aperture refractor. The old refractor is an equatorial mounted, 6-inch refracting telescope produced by W.M. Gaertner & Company, circa 1908.

The refractor tube and parts, laid out in the workshop.

“Initially, only the equatorial mount base, tube pieces, and some gearing was found and made available. There were no obvious markings on any of the steel or cast iron components that would help identify the manufacturer. Early on, it was thought to be a 6” Brashear or Warner & Swasey, since the 10.5” in the Tate rooftop (observatory) was of that well-known vintage. After engagement of the Antique Telescope Society community, it was properly identified as a turn-of-the-century 6” refractor manufactured by W.M. Gaertner in Chicago.”

The refractor, from the original W.M. Gaertner & Co. 1908 sale catalog.

Piecing the Parts Together

Founded by William Gaertner in 1896, W.M. Gaertner & Co. is now the Gaertner Scientific Corporation working out of Skokie, Illinois. Notably, the company made instruments for the nearby Yerkes Observatory, including spectrometers astronomer Albert Michelson, who pioneered early spectroscopy.

The quoted cost in 1908 for the 6-inch scope was $1,500 U.S., or about $45,000 adjusted for cost today, well out of an amateur observer’s price range. The cost suggests that the telescope was more something that a university might acquire.

“Many of the critical components of the telescope were still missing, so I needed to decide what to do. Since I am a mechanical engineer, I decided to completely model the parts that I do have in 3D CAD, so that I could then design and have fabricated the missing pieces. Too many critical parts were missing, however—especially the primary lens cell, control mechanics, and clock drive. After digging deeper within the storage areas of Tate Hall, nearly all of the critical components were eventually located. The primary lens cell was carefully stored by University of Minnesota researcher John Marchetti—also a friend and member of the MAS. The lens cell holds an air-spaced doublet achromat, and has a focal ratio of approximately f/15.”

The 6-inch primary objective lens in its cell.

The discovery of the crucial lens cell for the objective allowed the project to come together.

“After measuring and modeling every component down to the last screw, the 3D model was complete. The last remaining missing parts were the cast iron missing pier, the counterweights, the small finder telescope, and mechanical bits of the clock drive.”

Winding up the clock drive.

A Hand-Driven Telescope

Older German Equatorial mounted telescopes relied on a windup clock drive to move the telescope as it tracked the sky. Older telescopes weren’t just designed to be functional… they were also handcrafted works of art.

“I wanted to keep the telescope to the original color scheme—(with a) grey telescope tube and satin black mount, castings, and machined parts. I stripped and removed the original paint on all the component surfaces, removed dents and soldered the sheet-metal tubes where needed.

Then, I used a local machine shop to fabricate a few custom parts to finish the telescope. Since the main cast iron pier was missing, I fabricated a temporary pier from wood, so that the telescope could be used. The telescope was painted with enamel. I built a ‘tube rotisserie’ contraption that slowly rotated the tubes while painting so as to minimize paint drips.”

Then came the final assembly. The large metal tube for the telescope was huge, presenting a mammoth undertaking to hoist and mount into place.

Hoisting the tube into position.

“The cast iron mount base assembly weighs over 60 kilograms. The tube assembly weighs another 60 kilograms, and needed to be lifted in place over 2 meters in the air onto the pier. An engine hoist and block and tackle tied to our Catalpa Tree were used to hoist the parts into place. The weight-driven clock drive was installed and mechanically integrated into the Right Ascension worm gear drive assembly. Finally, the lens was cleaned up and installed in the front tube of the telescope.”

First (Second) Light

Finally, the time had come for the old refurbished refractor to see ‘first light.’ How does the refurbished telescope function under the night sky?

The telescope, fully assembled and refurbished.

“The 6” Gaertner telescope was carefully wheeled to the end of my driveway on September 3rd, 2023 under a warm and relatively clear sky. First telescope focus was achieved on the star Arcturus to the west. A crisp pinpoint reddish-orange star was seen. Along with some good friends from the MAS, a number of other objects were easily picked out that evening: The Messier 13 Hercules globular cluster with resolved into individual stars, the Double-Double (Epsilon Lyrae) was easily split into four stars, the Ring Nebula (M57), the Dumbbell Nebula M27, and finally, Saturn. The ringed planet was still low in the southeast, but showed its rings and handful of moons beautifully. The mechanical clock drive kept objects in the eyepiece all night long quite accurately and smoothly. Since the scope has a large focal ratio, fairly low-power eyepieces still resulted in decent magnification.”

Eyepieces typical of the era were of the basic Huygens 2-element design, easy to construct with a small apparent field of view.

Eyepieces, old and new.

An Astronomical Mystery from History

Of course, exactly where the telescope originated from over a century ago is still a bit of an astronomical mystery, though Valts has some ideas.

“The University of Minnesota had a small Students’ Observatory on the campus, built in 1891. It originally housed a transit telescope, chronograph and eventually the 10.5” Warner & Swasey refractor (later moved to the roof of Tate Hall). This Gaertner 6” telescope was not used in this observatory, as far as I can tell. So far I am not able to locate where this was originally housed.

Astronomy was an understaffed discipline in Minnesota for the majority of the 1900s. The department was usually run by a single professor—some of which included Dr. John F. Downey, Dr. Frances Leavenworth and later on , Dr. William Luyten (of Luyten’s Star fame). Luyten did mention the use of some instruments manufactured by Gaertner—but no mention of a 6” equatorial telescope. I still feel that Luyten may have had his hand on this telescope at one point, so my digging in the subject is ongoing.”

The Gaertner telescope, assembled in the workshop.

Why refurbish old scopes? When you look through an old telescope, you’re seeing the skies as observers of yore saw things. Valts has some other projects in the works as well.

“In addition to the 6” Gaertner telescope, I was given a handful of other items for restoration and exhibit. The original Fauth drum chronograph from the old observatory has been documented and restored. Another significant instrument is the glass plate analyzer made by Repsold and Sonne in Germany. An original Gaertner spectroscope and glass plate camera are also in my possession, awaiting restoration, as well as a number of original Gaertner eyepieces. The Fauth original transit telescope resides in the lobby of the Tate Hall observatory.”

What’s Next for the Gaertner Telescope

For now, Valts is looking for a good local home for the 6” Gaertner. “We hope to find a home for the telescope where it can be used in public outreach here in the Twin Cities area. Interestingly enough, I did find that right here in Minnesota, the University of St. Johns also has its own 6” Gaertner refractor sitting in their observatory unused because of its missing primary lens. Perhaps this will become a future project of mine…”

How many old scopes are out there, awaiting skilled hands to bring them back to use? It’ll be great to see the 6” Gaertner back in service once again, showing the public the wonders of the night sky.