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A helpfully peacemaking posting by Antoine stated-

" Douglas Denny and George are BOTH right on what seems an apparently 
Contradictary and irreductible statement/argument between them, with 
Douglass stating "The Height curve IS skewed" and George stating with equal 
force "the Height curve is NOT skewed, only displaced left or right". If you 
consider cases sufficiently close from LAN time and to an accuracy of 0.1 
arc minute for example, then the Height curve is NOT skewed as George points 
out, ... but if you deal with examples of heights sufficiently far away from 
Culmination time, then ODD terms will eventually come to play in some 
significant manner and the height curve when referenced to elapsed time IS 
definitely skewed."

============================

Yes, I would go along with that, with one quibble.

We are trying to combine together two graphs, that show
1) changing altitude due to Earth's rotation, if the declination was 
unchanging
2) linearly changing altitude due to declination change, if the Earth was 
not rotating, and it was permanently noon for the observer.

And we seem to agree that graph 1 is parabolic over a limited range, around 
noon, but eventually, well away from noon, higher-order terms will become 
important, so that curve will no longer be a parabola. But not odd terms, 
surely; only even ones, due to the exact symmetry of the geometry of line 1, 
before and after noon. Though I doubt whether that quibble upsets Antoine's 
overall conclusion.

=============================

By the way, listmembers might like to learn about the CD containing a 
collection of papers from "Navigation", selected because of their 
celestial-navigation context by David Burch, of Starpath (ex-editor of the 
late-lamented Navigator's Newsletter). The mouth-watering table of contents 
can be accessed at the IoN website at-
http://www.ion.org/publications/toc/celnavTOC.pdf

I bought my copy a couple of years ago, for which you didn't need to be an 
IoN member. I can't recall what it cost, except that it wasn't expensive, 
though the postage charges were.

And on the same subject, there's a DVD (or else a pair of CDs) which contain 
EVERY paper from the Royal institute of Navigation's "Journal of 
Navigation", from its inception in 1948 up to 2005. That's significantly 
more expensive (something like �70 to non-members, as I recall) but contains 
an awful lot of meat.

George.

contact George Huxtable, at  george@hux.me.uk
or at +44 1865 820222 (from UK, 01865 820222)
or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. 


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