Albert Van Helden

Saturn and His Anses

For Saturn alone stands apart from the pattern of the remaining celestial bodies, and shows so many discrepant phases, that hitherto it has been doubted whether it is a globe connected to two smaller globes or whether it is a spheroid provided with two conspicuous cavities or, if you like, spots, or whether it represents a kind of vessel with handles on both sides, or finally, whether it is some other shape.For Saturn alone stands apart from the pattern of the remaining celestial bodies, and shows so many discrepant phases, that hitherto it has been doubted whether it is a globe connected to two smaller globes or whether it is a spheroid provided with two conspicuous cavities or, if you like, spots, or whether it represents a kind of vessel with handles on both sides, or finally, whether it is some other shape.

Seventeenth-century telescope optics of Torricelli, Divini, and Campani.

Optics of telescope makers Torricelli, Divini, and Campani dating back to the 17th century have been tested interferometrically. It was found that the optical polishing technology had progressed to thorough control over the surface figure and finish, while the nearly paraxial conditions of the aperture remained constant. The instruments that were examined exemplify the knowledge of optics of that time, particularly with respect to the early use of erector units in terrestrial telescopes.

Cathedrals as Astronomical Instruments

The Sun in the Church Cathedrals as Solar Observatories. J. L. Heilbron. Harvard University Press, Cambridge, MA, 1999. 376 pp.

Book Review: Observations of Venus's 1769 Transit: The 1769 Transit of Venus: The Baja California Observations of Jean-Baptiste Chappe d'Auteroche, Vicente de Doz, and Joaquín Velazquez Cárdenas de León

35. ISBN 0-674-85433-0. Heilbron blends discussions of astronomy, religious architecture, and Catholic history to demonstrate that the Churchs efforts to establish an unquestionable date for Easter led to evidence on the geometry of the solar system that favored the ideas for which Galileo had been condemned.

Unmasking a Galileo Forgery

of the huge stone that supported its axis. This instrument was one of two made in England, and the Cape one was jarred on disembarkation. Later when it was sent back it was found to be fixed only loosely on its axis, but for decades its inconsistent readings baffled the South African astronomers and provoked learned correspondence from Airy at Greenwich, all to no purpose. Altogether the volume (which contains only very few errors of transcription from the original, often nearly illegible documents) throws a marvellous light on the daily lives and scientific collaboration of two strong and determined characters and their long-suffering wives.

The invention of the telescope

UNMASKING A GALILEO FORGERY A Galileo Forgery: Unmasking the New York Sidereus Nuntius. Edited by Horst Bredekamp, Irene Bruckle and Paul Needham. Vol. iii of Galileo s O, edited by Horst Bredekamp (Walter de Gruyter, Berlin, 2014). Pp. 102. euro49.95. ISBN 978-3-11-035464-5.In June 2004, Mara Miniati, then the director of the Museum of the History of Science in Florence,1 now known as the Museo Galileo, emailed me to ask if I would be willing to meet with someone who had a telescope allegedly made by Galileo. She was cautious, indicating that the optical system was not typical for telescopes in the Galilean era. I agreed to the meeting and was contacted by one Marino Massimo de Caro, who told me that he was a rare book dealer and had come into possession of a collection of Galilean items, one of which was a telescope.A few weeks later De Caro met me in Utrecht in the Institute for the History and Foundation of Science, where we were joined by my colleague Rob van Gent. The instrument in question was wrapped in an ornate red cloth, which we unrolled on the table of the Institutes coffee room. Two objects emerged. The first was a small spyglass, perhaps 25cm long, consisting of two tubes. It was a typical early seventeenth-century instrument; it magnified about five times and had a Galilean optical system. There were neither markings nor decorations to suggest any connection with Galileo.The other instrument, considerably more substantial, had a thick, ornate brass tube, about a metre long. On one end there was a slightly recessed convex lens, the objective, in an ivory mounting. At the other end, a horn mounting enclosed a small tube with three convex lenses. This was a compound eyepiece of the kind that came into use in terrestrial telescopes in the second half of the seventeenth century. If the instrument had first been made in the time of Galileo, then the original optics had been replaced.2 As I was examining the instrument, De Caro and I chatted. When I asked if he had had a good flight, he told me he had come by car, because the customs officials at Malpensa Airport in Milan might have prevented what was potentially a national treasure from leaving the country. The instrument would indeed have been a priceless legacy if a Galilean connection could be established.When I took the objective mounting out of the tube to check the focal length of the objective, I dropped it onto the floor. I was absolutely mortified, but luckily no damage was done. By this point, De Caro had heard enough to know that I was not about to say that this instrument had either been made by or ever belonged to Galileo. The meeting ended rather abruptly. The two instruments were unceremoniously wrapped in the cloth, and De Caro and his companion left. I promised to send him a report on my findings.De Caro looked like a reputable person and the vague story he told about the provenance of the two instruments sounded plausible enough. Was there a part of me that wanted at least the larger instrument to be authentic? The heavy brass tube made this instrument unwieldy, and I had never seen such a weighty seventeenth-century telescope. But it was in one piece, as are the two Galileo telescopes in the Florence museum. In my report to De Caro I wrote:This is the tube of an early seventeenth-century telescope in which the lenses were replaced sometime in the second half of that century. It clearly is a presentation instrument, and although the tube itself does not supply specific evidence of an association with Galileo and his Medici patrons, its shape and construction are highly suggestive. Its inclusion in this collection of Galileana offers further suggestions of such an association. Further research on this instrument is highly desirable.I never heard from De Caro again, and I forgot about the episode until I read newspaper reports in 2012 about De Caros arrest. That name rang a bell....In a brief period of time, perhaps starting in 2003 and ending in 2005, De Caro learned how to use new technology to forge old books. …