Monday, October 13, 2008

The Weekend - Antique Telescopes and Optics

One of the reasons to head off to Columbia, SC this last weekend was that friend Roger Ceragioli had an invitation to do analysis of telescope objectives, some of which approached 2 centuries old. Roger is a bit of an expert when it comes to antique telescopes as well as an expert optician, and there may be some interest in publishing research based partly on some of the examples that are housed in Columbia and environs.

The local telescopes of interest belong to Bob Ariail, who has bequeathed part of his collection to the State Museum there in Columbia. The museum itself is quite the gem. Built into a huge century-old cotton mill 20-some years ago, it is South Carolina's premier display of historical and scientific artifacts, as well as a showcase for traveling exhibits. It really is quite easy to spend a day there. Bob's telescope collection is quite extensive and evidently it is the aim of the museum to be a center of historical research in this area.

Besides the standard permanent display this weekend, they also had a traveling exhibit of working models of some of da Vinci's machines taken from his sketches, and a temporary display of movie artifacts and trivia of films made in South Carolina. They also had an ongoing celebration of the 20th anniversary of their opening with a harvest festival featuring crafts from local artisans, a stage with dancers, music and storytellers, and a "pig pickin'" bar-b-que. So besides visiting family and everything else going on, I really didn't pay much attention to Roger and his efforts, though we stopped and visited once or twice.

This was one of the store rooms far from the public area where some of the telescopes were stored and the location picked for Roger to do his work. You can see several examples of the standard brass-tubed telescope, most dating to the mid-19th century. My favorites, the long binocular-looking telescope, is newer - only about 100 years old, but are made by Zeiss and represent state of the art of the time, which all these scopes do, really.

Here, Bob Ariail (left) and Roger (right)examine a telescope objective, including a set of original eyepieces. Looking on at center is Tom Falvey, staffer at the State Museum, and primary archivist of these telescopes. All of these telescope lenses are actually doublets - two lenses of different glass types were put together with different curves to correct color errors inherent in most lenses. In those days, glass varieties were very limited, so some of the designs used to give good images are of much interest to collectors and fans of these instruments.

Here, Roger disassembles the lens components. He first uses a tester to examine the color correction of the assembled lens, then measures the curvatures, dimensions and accurate weights of the lenses to better estimate glass types and characteristics.

With the lenses now apart, they can be measured. In this one, the lenses were spaced by postage stamps that look to be from the 1960s or '70s, evidence that the lenses were at least disassembled and possibly worked on in that era. Roger admits that working with the crowd around him and with the wealth of examples, he didn't get as far as he wanted this trip. I suspect there is enough interest and further samples of telescopes to schedule him for a return visit.

1 comment:

Tuguldur said...

awesome report! that big binocular refractor is just unbelievable.

For the doublet lenses, they use one crown and flint glass to correct for chromatic aberration at some level, which we call the system to be achromatic. Nowadays we have doublets where one element is extra low dispersion glass or true triplet apochromats or even 4 element objectives to deal with aberration.