Henry Grey Posted December 22, 2022 Share Posted December 22, 2022 Saturday’s dawn caught Henry on the roof of the Octagonal Tower. He had woken up several hours before, and his servants had carefully loaded the three telescopes onto a coach, taken them to the Upper Ward of the Castle, carried them up five flights of stairs, and helped Lord Grey set them up, each on a small but sturdy table that would not topple easily. The servants had been under strict orders to make as little noise as possible, since most of the Castle’s guests were still sleeping, if they had gone to bed already, that was. Although all three astronomical instruments were of the reflective type, each telescope was of a slightly different design. The first was a design by the Scottish astronomer and mathematician James Gregory, who described it in his 1663 book Optica Promota. It employed a concave secondary mirror that reflected the image back through a hole in the primary mirror. That produced an upright image, useful not only for astronomy, but also for terrestrial observations. The second was a Newtonian telescope, built according to Isaac Newton’s 1668 design. It had a paraboloid primary mirror and a flat secondary mirror that reflected the light to a focal plane at the side of the top of the telescope tube, which made it convenient in confined spaces. Finally, the third instrument was a Cassegrain telescope, a design first published in a 1672 by Laurent Cassegrain. It had a parabolic primary mirror, and a hyperbolic secondary mirror that reflected the light back down through a hole in the primary. The folding and diverging effect of the secondary mirror created a telescope with a long focal length while having a short tube length. Due to using no lenses, none of the instruments suffered from the rainbow effect, and all had their advantages and disadvantages particular to each. After checking that the mirrors in each telescope had not misaligned in transport, by pointing the instruments to the morning star*, a process that took a while as the fog impeded visibility at times, the Baron sent his servants back to the house, but decided to stay on the battlements to watch the sun rise. It was going to be a beautiful sight. OOC: Venus, which is viewable with the naked eye both at dusk and dawn. Quote Link to comment Share on other sites More sharing options...
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