# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

### Compose Your Message

Message:αβγ
Message:abc
 Add Images & Files Posting Code: Name: Email:
Re: [9955]time of meridian passage accuracy
From: George Huxtable
Date: 2009 Sep 27, 15:41 +0100

```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
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.

--~--~---------~--~----~------------~-------~--~----~
NavList message boards: www.fer3.com/arc
Or post by email to: NavList@fer3.com
To unsubscribe, email NavList-unsubscribe@fer3.com
-~----------~----~----~----~------~----~------~--~---
```
Browse Files

Drop Files

### Join NavList

 Name: (please, no nicknames or handles) Email:
 Do you want to receive all group messages by email? Yes No
You can also join by posting. Your first on-topic post automatically makes you a member.

### Posting Code

Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
 Email:

### Email Settings

 Posting Code:

### Custom Index

 Subject: Author: Start date: (yyyymm dd) End date: (yyyymm dd)