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Total solar eclipse
Total solar eclipse (Des Loughney).

Next event:

Jul 7th
20:00, ASE, Church Centre, AUC
Dr Horst Meyerdierks, Astronomical Society of Edinburgh
Cassegrain – who was he?
Today the Cassegrain telescope design and its derivatives are the foremost technology for large professional telescopes and also for a significant segment of the amateur telescope market. It is surprising then that almost nothing was known about Monsieur Cassegrain for over 300 years. At the time his design was published merely as hear-say and faced harsh criticism by Huygens and Newton, the foremost scientists of the period. Although Newton's and Gregory's designs were realised in the 1670s, refractors remained the only practical telescopes for almost two further centuries. Around 1900, mirrors took over and grew larger than lenses ever could. Perhaps it is more remarkable that by then the Cassegrain design had not been forgotten altogether. We still know only very little about its designer. As a major advance, since 1997, we know his initial was not M (for Monsieur), nor N (for Nicolas, really for nescio or "unknown"), but his actual initial was L for Laurent.