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    Re: Latitude at noon.
    From: Frank Reed
    Date: 2010 Jan 31, 22:32 -0800

    George H wrote:
    "It was a bit of a surprise from such a careful celestial navigator, to discover that he doesn't really distinguish, when observing for latitude, between observing at Local Apparent Noon (LAN) and observing at maximum
    altitude."

    And Jeremy, you replied:
    "I think you misunderstand my post George. I indeed know the difference between LAN and maximum altitude"

    And just for the record, I am quite sure that most of the people who have read your posts, including me, know very well that you know how this all works.

    You wrote:
    "which was my point. The whole issue arose from the QMOW manual that instructed the navigator to arrive on station 10 minutes prior to calculated LAN. This practice is to allow ample time to observe the sun to rise and then "hang" to take the sight."

    I think that most of these books are trying to keep to a certain historical continuity, recommending "latitude by Noon Sun" according to traditional rules because it is a time-honored technique. They don't worry much about accuracy or modern improvements in understanding how it should be done.

    You added:
    "In this case, the speed and simplicity of the reduction trumps any errors in latitude."

    Yes. Definitely. It requires minimal tables and minimal calculation.

    You wrote:
    "Henry spoke of the universal LOP method for all observations. In other words: "Why not do away with the noon sight altogether?" I have a hard time arguing against this idea these days. Since the whole traditional reason for the noon sight was to get a reasonably accurate latitude having only rough ideas about your longitude and time, while maintaining a very simple reduction form; why do we persist in its use? In today's era of modern tables, navigation calculators, and computers, the use of LAN, instead of creating a simple LOP as we would for any other sunline, is not efficient."

    I think you will find that people have been saying exactly this for fifty years. Noon Sun has continued for reasons of historical continuity and ease of use. But for a navigator who has the tools and the skills to work out any LOP, there is no need for it. Any sight yields a line of position. Likewise, you can easily argue that there is no need for special Polaris sights. Certainly the procedure for Polaris sights outlined in the Nautical Almanac is pointless.

    And you wrote:
    "Still I don't see enough people either agreeing with my assessment of the whole observation to abandon the tradition noon sight; or going to the mathematical trouble of correcting the sight when observed at maximum altitude to shift the paradigm. We have enough trouble convincing people that longitude can sometimes be obtained with reasonable accuracy at noon."

    So we educate them. :-) Part of the problem here is that some people continue to insist that it is very difficult to make such corrections when in reality it is quite easy. In many cases, celestial navigation fans are fans (fanatics?) because they get a personal kick out of its intricacy, a little thrill out of being the only guy on the block who can work a problem in spherical trigonometry. To discover that you can get a complete fix in latitude and longitude without doing any spherical trig or learning any special tables to them seems like a personal affront --an assault on their specialized knowledge. For those folks, the idea of "easy celestial navigation" is offensive. But for most prospective students, it's the best news they've had all day!

    You concluded:
    "These days at the academies, celnav is rapidly losing importance in the curriculums, so that in short order, professional navigators will have only a basic knowledge of the sextant and the standard LOP and any more detail will have to come from extracurricular studies."

    We're already there. Apart from a "rite of passage" in maritime education, celestial has little relevance, and the majority of graduating students are well aware of that fact.

    And also:
    "I am afraid that the LAN observation will soon go the way of the time sight."

    I'll turn that around and predict that Latitude and Longitude by Noon Sun will soon be the ONLY type of sight worked by hand. Tables like H.O.229 will fade into history as those few who work LOPs complete the switch over to electronic calculation (a switch that began decades ago and is really already 99% complete). But Noon Sun will be around forever. Well... we can hope, right?

    -FER


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