NavList:

   

Reply

On 2011-08-19 16:22, Frank Reed wrote:
> In any case, when I thought it through a bit further I got right back
> to square one. If we limit ourselves to any pair of lunar distances or
> in my hypothetical case, any pair of stars sitting right on the Moon's
> limb, the observations uniquely determine the Moon's topocentric
> position in the sky (well, really there might be two solutions but
> widely separated so no issue to distinguish them).

Right. Since this is question of geometry and what has been posted
against it so far are number games where I have neither  seen the
(intermediate) numbers nor the underlying algorithms, anyone can guess
which side I am leaning towards.

> But this still leaves us with the problem that the "black box"
> solutions say otherwise. Clearly Dave W. and Harri and Peter are
> solving somehow for GMT and position at the same time, but it's highly
> sensitive to the exact position data and the exact model specifications.

Dave's refraction-free topocentric distances are not even consistent
with each other to arc second level. Ex falso quodlibet. I have asked
from which point they are supposedly measured.

Harri used refracted distances and stated that he used the same N.A.
approximation formula that had presumably been used to generate them.
His solution, if otherwise correct, is therefore entirely based on
differential refraction. He concluded that the problem is "doable in
principal".

Indeed, "in principal", whatever that means.  "In principal",
Aristarchus found the distance of the sun by measuring its angular
distance from the moon at half moon. "In principal", Ptolemy was able to
determine the moment of solstice by observing the shadow of an
equatorial ring. "In principal", Halley was right to think that one can
find longitude from compass variation.

Herbert

   

Reply