Dennis Lee Bieber <wlfr...@ix.netcom.com> on Sat, 12 Oct 2019 12:26:43
-0400 typed in comp.lang.python the following:
>On Fri, 11 Oct 2019 20:41:47 -0700, pyotr filipivich <ph...@mindspring.com>
>declaimed the following:
>
>
>> I've been hacking around with what needs to be computed. As in
>>"okay,the orbits have different speed at different points on said
>>ellipse, and so ummm, what does that do to sidereal time?" And so
>>forth.
>>
>> And as I've said, "How did they do this without a mechanical
>>clock?" I really need to look that part up _first._
>>>
>
> Water clocks go back centuries
>https://en.wikipedia.org/wiki/Water_clock and sundials were used for
>daylight (since noon is when the shadow is shortest it is an easily
>determined point, and one could then calibrate a 24+hour water clock by
>comparing noon to noon).
>
> But that said, those ancients also believed in a geocentric universe,
>and started adding epicycles to the cycles of the planets to account for
>the apparent retrograde motions -- their idea of the planet orbits begin to
>look like things created with spirographs.
>
> For more advanced (heliocentric orbits)... Like comets, say... One did
>angular measurements against the "fixed stars" and sidereal time (what star
>is overhead "now" measured from some declared 0 point -- first point of
>Aries, say, which is overhead at night in September [in April the /sun/ is
>overhead when it is in Aries]) cf: Angles-Only Orbit Determination (vs
>range-only, or range&angle, both of which need either radar or multiple
>observations from different locations on the earth [parallax computation to
>determine range])
>
> The star XYZ is at zenith and the wanderer is x-deg west and y-deg
>south of it. Next night star XYZ is at zenith and wanderer is x2-deg west
>and y2-deg south. Though one may not need to wait for zenith, if one also
>measures the east/west angle for star XYZ relative to the observer zenith
>[to determine time relative to the zenith passing].
Thanks, that clarifies things a bit. I'd figured that was some
thing on how it would go.
--
pyotr filipivich
The question was asked: "Is Hindsight overrated?"
In retrospect, it appears to be.
--
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