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    Re: Emergency sun declination
    From: Doug Royer
    Date: 2004 May 21, 16:18 -0700

    You betcha.It's 23.5* though as Frank pointed out.
    Here's what I got in a few minutes useing a rose and the "graphic" method:
    The date's(05-21)number of inches on the vertical axis = 3.3 in.
    The vertical radius length = 3.81 in.
    3.3/3.81 = 0.86614
    23.50 x 0.86614 = 20.3543* = 20* 21.3'
    dec. = 20* 21.3'N
    05-21-04 1601zt sun dec = 20*24.1'N
    Not to bad for 3 minutes from start to finish.That includes marking the
    rose.Good enough for an emergency.
    Let's try the below:
    61 days since the equinox. 05-21 - 03-20
    sin(61) = 0.8746
    23.5 x 0.8746 = 20.5531 = 20* 33.2'
    dec = 20* 33.2'N
    In the ballpark.
    Good enough to use if one had no idea otherwise.
    
    
    
    
    
    Ahha,
    
    A graphical method of computing the sine of a function.  Sine is
    opposite over the hypotenuse. #3 =opposite, #4=hypotenuse.  Then dec =
    22.5*sine(days past vernal equanox), etc for other seasons.
    
    Fred
    
    > 1.Take a parrallel rule and from the horizontal axis,makeing sure it
    > stays
    > parrallel with that axis,move the rule up to the date's point on the
    > arc.
    > 2.Draw a line from that point to the vertical axis.
    > 3.Measure the distance from the line thus drawn to the point where the
    > vertical and horizontal axis's meet in the center of the rose.
    > 4.Measure the distance from the center of the rose to the edge of the
    > arc.
    > 5.Divide the "date measurement"(#3) by the total radius
    > measurement(#4)to
    > get the ratio of the two.
    > 6.Multiply that ratio by 22.50*(degree)
    
    
    

       
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