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    Re: Quick Estimate of Sun Declination: analemmas?
    From: max mulhern
    Date: 2018 Apr 6, 06:47 -0700


    I love the concept of creating one's own  tables of GHA and declination on the fly. When I was sailing to Bermuda last June I even tried to draw my own azimuthal equidistant projection for 37°N to explain a sun moon relationship (as I recall it was around 5 EDST with a rising sun and a waning moon that appeared to have reciprocal azimuths). However this projection was more like an artistic rendering.....

     As for the analemma I agree that your graphing method is much easier to create.  In class,  but especially on the water, I  do ask students to calculate mentally what the declination is for the day. Next time I will ask them to graph their way to an answer.

    You asked "Why did globe manufacturers put annalemmas on their globes?" I don't know either but will look into it. Was it to enable the English to wear Solar Toupés? I will go look at an origianl Mercator Globe and see if there is one on that.  I do know that the analemma was originally the sundial  and according to  the Merriam Webster :"from Greek analēmma, lofty structure, . . . "

    Is there  a relationship between the sign for infinity and the analemma?

    How many navigators know  that if you take the graph of the equation of time (on translucent paper) and fold it in half such that the first 6 months of the year are superimposed on the last six months that you get an analemma? I don't know when the first sinosoidal  waves were graphed. . My hunch is that it was when the Geeks were using the cone to create, among other things, parabolas. The analemma is an odd one with its dip in the middle ... In any case I cherish it as a means to get a relatively accurate Noon Sight in the abscence of a Nautical Almanac. . 

    Speaking of cones I was thinking of Native American Tipis and wondering if they ever traced the the daily curve of the sun on the inside of their shelters? I have found nothing online  to suggest that they did.

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