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    Re: Lat/Lon by "Noon Sun"
    From: George Huxtable
    Date: 2009 Apr 14, 18:19 +0100

    Although Geoffrey Kolbe's posting, in [7837] , appears to differ greatly 
    with my own, it seems to me that the difference between us is rather less 
    than he makes out.
    
    I have no great argument against "navigation around noon", as long as it's 
    kept in its proper place. It is indeed a valid tool in the navigator's 
    workbox, and under the right circumstances can provide  useful answers, as 
    long as its deficiencies are recognised. It is, in almost every respect, 
    inferior to traditional position-line navigation, with only one thing to be 
    said in its favour; that it is intellectually undemanding.
    
    If it's taught to students as part of a syllabus that includes all the other 
    necessary stuff for proper navigation, then well and good, as I said before. 
    Geoffrey wrote-
    "Having graduated from the "Frank Reed school" and my interest aroused, I 
    then went on to gain "a rounded understanding of position lines and sight 
    reduction, how to read a nautical almanac, how to use the Moon or take a 
    twilight round of star observations..."  I ask Geoffrey whether, before 
    going on to gain that "rounded understanding", he considered himself 
    competent to "navigate successfully and safely around the world". I hope 
    not, because if he did, that's where danger lies.
    
    Geoffrey continued- "Frank's point, though, is that it was not necessary to 
    go on and do the post-grad course to be able to navigate successfully and 
    safely around the world - provided the limitations of the method are born in 
    mind. But that is true whatever method is used." What I complain of, in 
    Frank's many postings on this topic, is that such limitations have been 
    minimised, or dismissed, and it has fallen to sceptics such as me to point 
    them out.
    
    My interpretation of Frank's postings on this subject has been that it is 
    being proposed as an alternative to position-line navigation, not as an 
    adjunct to it. If I have got that wrong, I hope Frank will put me right, and 
    he would then deserve an apology. It would be interesting to see what a 
    syllabus for a Frank Reed navigation course would include.
    
    Geoffrey asks- And why should a generation of navigational incompetents 
    arise because one person chooses this particular method from the long menu 
    available of CN methods and finds it to his liking? To say that they will 
    "quickly become lost at sea" by being such a "one club golfer" is gross 
    exaggeration George, as I am sure you know. "Celestial Navigation" is 
    actually done as a check on dead reckoning. If the sun does not shine for a 
    few days, it just means the uncertainty in your position grows. It does not 
    result in you being "lost at sea".
    
    Living where Geoffrey does, in the Scottish Borders, that attitude surprises 
    me. His climate is similar to mine. We get cloudy skies. The Sun is 
    available only about a third of our daytime (at my guess). A celestial 
    navigator gets by, by snatching appearances of the Sun within broken cloud, 
    when he can. The days when the Sun appears for an unbroken hour around 
    midday are few and far-between, and this is a common state of affairs in 
    higher latitudes. Things may be different in the Med, in Florida and the 
    Caribbean. Geoffrey may think that DR will substitute, but not to a 
    navigator entering the Western Approaches after an Atlantic crossing. He 
    needs an observation.
    
    Geoffrey wrote- "I think that the point was made four years ago that in the 
    latitudes at which, and the seasons in which, people usually go sailing 
    recreationally, Frank's claimed accuracy was reasonable." Aha! Is that an 
    accepted limitation, then? How are those limits defined? Prospective users 
    should be told.
    
    "Frank did say that if an analemma is used for the equation of time, its 
    scale should be "sufficient".". No. The words were these, about the Nautical 
    Almanac-  "you don't need one at all --only a short table of declination and 
    equation of time, possibly graphed as an "analemma" perhaps " Let's think 
    about that. If Frank is going to meet his claim of no more than +/- 2 
    minutes in latitude, I think he and I would agree that any error greater 
    than 1 minute in predicted declination would be unacceptable. Declination 
    varies over a range of 47�, and changes at up to 1' in each hour. If that's 
    going to come from an analemma, it would be necessary to read it to one part 
    in 3000 of its span, and to read off a particular date-and-time, to the 
    nearest hour, around a loop which occupies a year. Can't be done.
    
    George.
    
    contact George Huxtable, at  george{at}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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