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On Dec 15, 2005, at 3:20 AM, Frank Reed wrote:

> Put the laser where your eye belongs when
> using the sextant, and the rays  that the laser emits correspond
> *exactly* to the
> rays that your eyes would  receive from a distant source --they're
> just
> travelling in the opposite  direction at every optical surface (or
> a bit more
> physics-y, they're all  time-reversed).


It's nice to know that we can reverse time by pointing flashlights
into the eyepieces of our sextant telescopes! ;)

An elf told me that Santa might leave a laser level in my stocking
this Christmas.  I look forward to seeing any more sextant laser
tricks.  I can envision being able to determine arc errors if one had
a flat wall to which the sextant could be pointed at right angles to
some point (normal to the point), but my physics knowledge is
insufficient to implement such a test in the time available (or to
assess whether it's feasible and accurate).  I would suppose that an
accurate assessment of parallax would be a necessary component of
such a test.

Fred

   

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