Newbie needs book advice

[Roy Smith]

"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.

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Steve,

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.

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