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    Re: Sine curve to approximate declination
    From: Frank Reed CT
    Date: 2004 May 31, 22:22 EDT
    Last week, George H wrote:
    "I detect a certain amount of wriggling here by Frank Reed, in his response
    to Trevor Kenchington's objections, and mine, to the "broader shoulders" he
    gives to the variation of declination."

    All I can say is that that is a pointless comment.

    And:
    "We all were (weren't we?) discussing how the declination would vary with
    date-of-year"

    We were discussing lots of things. It is a common occurrence that a group of people can be talking about the same subject --exactly the same subject, so they presume-- and then discover as they go that they are discussing slightly different aspects of the same subject. I'm sure you're familiar with this phenomenon.

    Over the years that I have been teaching astronomy and navigation topics, I have heard a number of people say something like "the Sun's declination makes a sine curve" (often at the beginning of a discussion of an approximate way to calculate declination), and I usually ask them what they mean. With few exceptions, they point to the ecliptic on a star chart like the one in the back of the "Nautical Almanac", which --of course-- is a graph of declination versus right ascension. It does resemble a sine curve, but it's a little different. Does that help you to understand how we might be talking about two slightly different things?

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