On 01/11/2017 07:02, Gerald Kelleher wrote:
On Tuesday, October 31, 2017 at 7:10:10 PM UTC, palsing wrote:
On Tuesday, October 31, 2017 at 12:02:46 AM UTC-7, Gerald Kelleher
wrote:

RA/Dec is an extension of the 24 hour system...

This just wrong in many ways, the RA/DEC system that we use is
based on an extension of the Earth's axis of rotation, hence the
name equatorial coordinate system.

I am afraid not Paul for the reason presented many times, the
Lat/Long system required the construction of a meridian line to
accurately determine the moment when the observer and his location
were midpoint to the circle of illumination at noon. All observers
along that meridian,irrespective of season or hemisphere, experience
noon at the same time so the application of the Equation of Time
rendered natural noon into 24 hour clock noon . If the observer was
on a ship at sea he could then determine his location to any other
meridian and any location on the planet as time difference equates to
geographic separation.

Until there was a reliable means to keep accurate mechanical time on
board ships observations of the sun were useless for determining
longitude. There were quirky ways promoted by the then Astronomer Royal
Neville Maskelyne that involved mutual events of Jupiters satellites or
the lunar distance method which he published in 1763. They were quite
difficult methods to use in practice though on a rolling ship.

https://en.wikipedia.org/wiki/Lunar_...ce_(navigation)

Even as late as the 1900's good marine chronometers for ocean going
navigation cost a significantly large sum of money. They have held their
value quite well too:

http://www.onlinegalleries.com/art-a...%20chronometer

direction will give you the same result so don't fool yourself into
equating celestial sphere rotation with daily rotation,at least not
directly.

Celestial sphere rotation of the fixed stars *is* a pure rotation.
(if you ignore nutation and precession)

The stars return to the same place in the sky as regular as clockwork.

It is the elliptical orbital motion of the Earth around the sun that
makes the solar motion across the sky vary in speed. And the moons
orbital motion around the Earth even more complicated. Something known
to the Babylonians and everyone educated since apart from you.

--
Regards,
Martin Brown