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Newbie needs book advice
Roy Smithroy at panix.com
Mon Apr 16 08:34:16 EDT 2001
"Steve Holden" <sholden at holdenweb.com> wrote:> An ephemeris is a chart of planetary positions at certain times, used (among> other things) to construct horoscopes.M-X Soapbox-ModeSteve,You do astronomy a disservice if the only example of the use of an ephemeris you can come up with is horoscopes. That's kind of like saying python is a cool language because you can use it to pick Zippy The Pinhead quotes randomly out of a file.An accurate table of planetary motion is essetial for celestial navigation (i.e. figuring out where you are with a sextant and chronometer). Up until WW-II, this was the ONLY way sailors (and aviators) out of sight of land could know where they were. Polar explorers, too. Since WW-II, electronic navigation systems have slowly reduced the importance of celestial, but it continued to be an important skill up until the past decade or so, when GPS really made it obsolete.In fact, an ephermeris is really a table of positions of any body in space, not just the planets. The GPS system itself depends on the receivers having an accurate ephemeris of the satellite orbital positions.We would have never put a man on the moon without an accurate ephemeris. Nor been able to send probes to visit other planets in our solar system.M-X Soapbox-Mode-Off
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