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    Re: Perpendicularity check
    From: Frank Reed CT
    Date: 2004 Sep 22, 23:08 EDT
    Alex E wrote:
    "I can report some Sun, Moon and stars measurements which I made
    from my balcony under the ideal conditions, with an artificial
    horizon. These measurements seem to show errors
    of about 0.4' (for the Sun) but I do not have an Almanach yet;
    I am using the "Complete on board Celestial Navigator" which lists
    the Sun position with only 1' precision. I hope that more precise
    Almanach data will permit me to explore the ultimate sextant

    I have put together a very accurate Nautical Almanac tool on my web site. It can display almanac data for the standard navigation objects accurate to about 1 arcsecond for the period from 1750 to 2050. The main address for the various tools is

    So far, I have found no other software almanacs which are as accurate. Another popular online Nautical Almanac has been assembled by Omar Reis. It's not as accurate as mine, but it is set up to look visually like the pages in the published Nautical Almanac, and some people prefer that formatting. Omar Reis's online Nautical Almanac is located here:

    By the way, I think the "Complete On-board Celestial Navigator" is very clever, and its accuracy is sufficient for the realities of standard late 20th century position line navigation.

    Frank R
    [ ] Mystic, Connecticut
    [X] Chicago, Illinois
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