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Restoration of two Clark refractors.

IT SEEMED the chance of a lifetime. In September 1991 I purchased a vintage 6-inch f/15 refractor -- an instrument made by Alvan Clark & Sons, the telescope-making firm widely regarded as foremost in the world early this century. Included with the scope was a crate for the tube assembly, the original tripod with leather straps, a metal pier for installation in a permanent observatory, and an equatorial mounting with a spring-wound drive.

As I picked up these items, the previous owner, Regina Giessow of St. Louis, Missouri, recalled other small parts. Four months later she came across a box marked "Christmas decorations." It proved to contain seven eyepieces for powers from 75x to 450x, a star diagonal, a Sun diagonal (also called a Herschel wedge), a solar eyepiece filter, and an eyepiece box.

The telescope's tube is solid brass. The 6-inch objective is an achromatic doublet, as is the 1 5/8-inch finder objective. The eyepieces are all of the Huygens type -- a two-element design that, while primitive by today's standards, performs surprisingly well with f/15 optics. These eyepieces have brass barrels 1 1/8 inches in diameter, the Clark standard.

The equatorial mount is quite elaborate, including silvered setting circles and vernier scales with movable eyepiece magnifiers. But I quickly realized that the mount and scope were not meant for each other, because the tube bolts could touch the setting circles when the telescope was aimed in just the right (or wrong!) position. I made an extension for the declination shaft to correct the problem.

Indeed, the mount is something of a mystery. At first I thought it was a Mogey, but when I displayed the instrument at the 1993 meeting of the Antique Telescope Society in Williams Bay, Wisconsin, I heard other opinions. Peter Serrada, an expert on the Mogey firm (S&T: January 1990, page 98), thought it was a Byrne instead. Others agreed. Yet the weights, setting circles, and eyepiece magnifiers look like Clark parts. The mount may be a mixture -- we may never know for sure.

Only one original tapered brass foot remained on the tripod legs, so I made three new ones. I also made new steel pins that dig into the ground. The tripod did have the original leather straps that joined the legs at the center, but they were rather stiff. Soaking them in neat's-foot oil for two weeks softened them up nicely. While the clock drive was intended to be mounted on the pier, I made a bracket so the unit can be used with the tripod as well.

Both the main tube and the finder were covered with four coats of paint that ranged from green to blue. The outer layer's color was olive drab, which makes me wonder if this telescope served time in the military. Or was this shade just paint that had been on hand? Why was a brass tube in excellent condition painted in the first place? Only the faceplate of the tailpiece was left unpainted.

Removing this paint presented several problems. What kind of stripper or other technique should be used? What tools could I safely use without marring the metal underneath? After discussing the matter with representatives at several chemical companies I chose Bix-brand stripper. Steve Sands, a fellow member of the St. Louis Astronomical Society (SLAS), helped with this messy operation. We used a Teflon scraper to remove the sludge of paint and stripper because, unlike a metal scraper, it would not scratch the brass.

The first few inches of freshly stripped tubing held a surprise. Under the paint was some writing in pencil: "62 - 39 = 23." Right away we wondered what other inscription or signature might come to light! Unfortunately, the rest of the tube contained nothing but a lot of tarnish under the paint. We washed the metal with paint thinner to remove the stripper, then with alcohol to remove the thinner.

Before we polished the tube I made phone calls and did a lot of research to determine what technique would be appropriate. No buffing wheels, wire brushes, steel wool, or the like should ever be used on old brass. These harsh treatments inevitably round over edges and knurling, remove machining marks or engraved lines, and in general destroy the original look. Instead we employed Nevr-Dull (a polish-impregnated cotton product) and Brasso polish. They removed the tarnish. We didn't try to make the tube look like a glossy new one, because it isn't. The marks and nicks that we left belong to the scope's unknown past. The tube's interior has six baffles to block reflections, and we repainted them flat black.

To retard tarnishing I applied clear acrylic lacquer to the tube. However, I am looking for a product closer to the gold lacquer or straw finish that the Clarks might have used. Restoring the clock drive wasn't nearly as hard as working on the tube. I do clock repair as a business, so I already had the necessary skills and tools.

While occupied with these activities I sent the objective lenses to D & G Optical to be cleaned. This firm installed new spacers between the elements and found some original rouge on the edges, which was left undisturbed.

I stripped the rest of the metal parts, then primed and painted them with gloss black enamel. Several missing pieces had to be fashioned. I made cabinet-head bolts for the tripod, a new screw for the focuser knob, several thumbscrews, and an adapter for 1 1/4-inch eyepiece barrels. I also made the missing half of the universal joint in the declination control.

I marked all new or replaced parts with a distinctive, star-shaped stamp so that future restorers can tell at a glance which pieces are not original. Instead of altering any existing parts, I made all replacements to fit. Thus the instrument can easily be returned, if desired, to its state when I got it.

Readers who contemplate a restoration like this should take lots of pictures ahead of time. Better yet, make a narrated video. It is easy to become confused about how the parts go back together. For example, in my instrument six screws hold the right-ascension plate to its wheel. When originally installed the projecting ends of these screws had been filed off flush. Even though all six screws are about the same length, each one fits perfectly only in the hole it came from -- something quite tedious to determine by trial and error!


I keep everything I know about the history of the scope in the tube crate so it will be there for the next owner. This includes a record of my own restoration. For example, attached to the crate were several old tags. I showed the ones I couldn't fully decipher to a paper restorationist, and he was able to recover a little more information.

Regina Giessow told me everything she knew about the history of the 6-inch refractor. Her late husband, Fred, had purchased it in 1959 from the astronomer Robert Hardie. I wrote or went to the schools and colleges where Fred had taught and interviewed his colleagues.

Regina told me how she and Fred had rented a trailer to pick up the 6-inch at Vanderbilt University in Tennessee, where Hardie was teaching. He had probably bought the telescope from George Slack, another name I found on one of the crate tags. Slack lived in Duluth between 1942 and 1949. These tags indicate that he purchased the scope in January 1942 from M. Rasmussen of Amsterdam, New York, a one-man shop that sold quite a few telescopes through ads in Sky & Telescope. One of the labels contains a declared value of $1,617, about right for the World War II time frame.


While I was following up these leads the secretary of SLAS came across a note in an old file cabinet. It was a "while you were out" message, dated September 8, 1981, and it said "Call about Clark telescope." I seriously doubted that the phone number belonged to the same person after 11 years, but soon he and I were chatting about the brass tube, crate, Sun diagonal, tripod, and the fact that the Clark telescope had come from the St. Louis area. Only after several minutes did we realize we were talking about two different Clark telescopes! He had a 4-inch.

My second chance of a lifetime came in June 1993 when I acquired this 4-inch Clark instrument as well. The previous owner had bought the scope at a flea market 12 years earlier mainly for an investment. There is no way to trace its history now, but he told me that the late Robert E. Cox had checked it out for him and made a 1 1/4-inch adapter so that modern eyepieces could be used. This instrument has the original tripod, a Clark Corporation No. 5 mount, storage chest, lens caps, terrestrial eyepiece, slow-motion rods for both right ascension and declination, and several more accessories.

Its tripod was missing all the brass pieces and the steel pins on the bottom of the legs, so I had to make them. There were no leather straps, so I got some made and had the name A. Clark tooled into the leather. I made a brass triangle, similar to that on the larger tripod, to hold the belts together between the legs.

The 4-inch refractor is something I can set up myself -- unlike the 6-inch, which takes two people. I was struck by the similarities and differences between the two instruments. The 4-inch lens cell is not adjustable, while that of the 6-inch has push-pull screws.

While the early history of both instruments remains obscure, Clark experts Robert Ariail, John Briggs, and Kenneth Launie have helped me estimate the manufacture date of the 6-inch as about 1930. The 4-inch is somewhat older, probably about 1923. Ariail, by the way, has been working with Deborah Jean Warner of the Smithsonian Institution on the revision of her 1968 book, Alvan Clark & Sons: Artists in Optics. The new edition is due to be published this year by Willmann-Bell, Inc.

If any reader can shed more light on these instruments or their early owners, please let me know!

JON SLATON 1025 George Alton, IL 62002
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Title Annotation:Telescope Making; Alvan Clark and Sons
Author:Slaton, Jon
Publication:Sky & Telescope
Date:Feb 1, 1995
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