Fathers of the Telescope

The Church and the Early Telescope

On October 29 2002, the Public Broadcasting System of the United States first aired a biography of Galileo titled "Galileo's Battle for the Heavens". The program's accompanying website stated "...Despite myriad embellishments, however, most optical telescopes in use in the 21st century derive from the two types developed in the 17th century by Galileo and Newton, on whose shoulders all astronomers, both amateur and professional, stand today.". Most optical telescopes used by serious amateurs and researchers today derive from two types developed in the 17th century...but not by Galileo and Newton. They actually derive from the two types of telescopes developed by Christopher Scheiner and Laurent Cassegrain, both 17th century Roman Catholic priests, and Johannes Kepler, the great astronomer. In fact, the Galilean telescope was a dead-end and its popularity amongst astronomers barely outlived Galileo himself. Most research telescopes today are Cassegrain reflectors, although some of the largest telescopes can behave as either as Cassegrainian or Newtonian reflectors. The irony here is that the writers of the biography had clearly portrayed the church throughout as 'battling' science. It should surprise no-one that the priests' contribution to the development of the early telescope was never mentioned in the program or on the accompanying website (see Galileo's Battle for the Heavens).

The Matthew Effect is a tendency discussed by historians where credit for discoveries or inventions is incorrectly attributed to already famous scientists. There is probably no better example of this effect than the history of the early telescope. There were many scientists who made critical contributions to the development of the early telescope (see Timeline of the Telescope). Popular histories typically only discuss two, Galileo and Newton. Those excluded include famous thinkers such as Kepler and Descartes and several Roman Catholic priests.

There were several advances in theoretical optics and telescope construction during Galileo's lifetime that would impact the development of telescopes for centuries to come. Oddly, Galileo was not involved in any of these advances. His importance to the history of the telescope lies in the fact that he made the use of telescopes respectable in science. This on its own is a very important contribution. He was also able to make superior telescopes for his time. Florence, Galileo's home for much of his life, had been the pre-eminent center for lens-making in Europe since the late thirteenth century (see Timeline of the Telescope Year:1289). Venice, a short distance from Galileo's home in Padua, was also noted for lens-making. Galileo and his benefactors would order hundreds of lenses at a time and select a handful of the best for making his telescopes. Beyond these two achievements, it is difficult to name one advance made by Galileo in the theory or construction of telescopes that is in use today. That is not true of the church scientists of his day; especially the Jesuits.

The scientists who had the greatest influence on the future of optics and telescope construction from Galileo's day were Johannes Kepler, Rene Descartes, Wilebrord Snell, Father Marin Mersenne, Father Bonaventura Cavalieri, Father Christopher Scheiner and Father Christopher Grienberger. The first three developed a theoretical foundation for refraction and reflection that would be built upon in the following centuries. The four fathers made critical contributions to the technology of telescopes. All of their contributions are still in use today. Fathers Marin Mersenne and Bonaventura Cavalieri together would propose the basic geometric shape that would be used in modern (reflecting) research telescopes (see Reflecting on History). Father Christopher Scheiner, a Jesuit, would be the first to construct a modern astronomical telescope, using theory proposed by Johannes Kepler. Christopher Grienberger, a Jesuit colleague of Scheiner's, would propose an extremely sophisticated method of mounting telescopes to better follow celestial bodies as they arc through the night sky. Father Scheiner would use Grienberger's equatorial mount to produce the finest celestial images of the early seventeenth century. The contributions of Father Nicolo Zucchi, another Jesuit, may not have been as important as the scientists listed above, but he was able to demonstrate that using telescopes combining lenses and mirrors was viable. This was in 1616, 50 years before Newton's famous reflecting telescope. He was the master craftsman who also built refracting telescopes for Johannes Kepler at the request of the Jesuit order (see Jesuits and the Telescope).

By the end of the seventeenth century, there had been some remarkable achievements in telescope making. The lenses of Giuseppe Campani have spherical curvatures as good as can be made today [_1_] . Giuseppe Campani had first come to public notice when he and his brother, Matteo (a Catholic priest and probably the finest clock-maker of the day), entered their telescope in a competition against the greatest telescope makers of the day. The telescope of the Campani brothers won. But the expertise of telescope-making was being spread beyond the few great telescope makers of the day. It wasn't spread by the most famous telescope makers. Campani, like Galileo before him, was very secretive about his methods and tools. It was a Capuchin Monk, Cherubin d'Orleans, who was instrumental in spreading this knowledge. Cherubin d'Orleans wrote two important works on optical instruments and optics, La Dioptrique Oculaire and De visione perfecta. In De Visione perfecta, he documents his invention of the binocular microscope. La Dioptrique Oculaire included detailed descriptions of the tools and techniques involved in the manufacture of lenses. Frank Twyman, in a modern treatment of lens and prism making, stated 'These descriptions are so good, and show such thoughtful personal knowledge of the subject, that they would be suitable to place in the hands of an optical apprentice today' [_2_] . The lathes he used for grinding and polishing were very sophisticated. An image of one of Cherubin D'Orleans lathes is shown below (modified from here).

The scientists working for the church may have had some advantages which may have allowed them to share their work more freely than others. There were many excellent telescope makers in the seventeenth century. For the most part, they were very secretive about their methods and if their secrets were released it was against their wishes. While their achievements were great, they did everything in their power not to contribute to the state of the art. This is understandable since their livelihood depended on it. The priest-scientists who were involved in telescope-making were in a different situation. They had the advantage of a guaranteed income, regardless of how modest it may have been. This might be why several of the most important published works on the making of telescopes from the seventeenth century were written by priests. Niccolo Zucchi, Cherubin D'Orleans, and Anton Rheita all published important works on telescope design and construction.

For the last one hundred years, almost all of the largest optical telescopes have a similar design known as a Cassegrain design. The Hubble Space telescope and the space telescope scheduled to replace it are also Cassegrain designs. Father Laurent Cassegrain, a french priest and contemporary of Isaac Newton and Cherubin D'Orleans, was the first to propose this popular design. In an ironic twist that is so common in history, Isaac Newton was one of the leading critics of the young priest's design. Here is what Newton had to say about the Cassegrain design:

You see therefore, that the advantages of this design are none, but the disadvantages so great and unavoidable, that I fear it will never be put in practise with good effect [_3_] .

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