Newbie needs book advice

[Steve Holden]

"Roy Smith" <roy at panix.com> wrote ...
> "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-Mode
>
> 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.
>
Pardon me. My purpose was not to serve astronomy, a science which has many
times proved itself quite ccapable of blowing its own trumpet. I am aware
that horoscopes are not the only use of ephemerides (hence my use of "(among
other things)" in my original post).

I presume you are professionally involved in astronomy. Strange how you only
climbed on your soapbox when someone mentioned astrology, an art rather than
a science, but old as astronomy, if not older. So how was your wish to
educate triggered?

This is not atypical, of course. The science of astronomy has, as a body,
attempted to discredit astrology for a long time. I won't speculate on the
reasons, which aren't important to me since I am not involved in either
activity.

> 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.
>
I stand corrected.

> 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
>
I should think so, too. Just the same, ephemerides *are* used to cast
horoscopes, even though astronomers might prefer it if they weren't.

but-it-*does*-move-ly yr's  - sTeVe