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    Re: formula for refraction
    From: Bill B
    Date: 2007 Mar 23, 16:41 -0400

    
    > From: "Frank Reed" 
    > You changed one too many ones to twos when you edited the formula:
    > toward the end, you've got "INT(B2)+2" where it should be "INT(B2)+1".
    > That seems to be the only problem.
    
    Thanks, that took care of the problem.
    
    > And you asked:
    > "As a follow up, what is your opinion of the Saemundssen quoted in
    > Meeus for Hc to H (below) as opposed to 57"/tanH"
    >
    > Well, I'm not quite sure what you're asking here. Those are not used
    > for the same purpose.
    
    Understood.  If I understand the former is for refraction from Hc to H, the
    other for H to Ho.  The problem I have using H to Ho refraction adjustments
    is the guessing game that can occur when working backwards.  A real concern
    with low elevations, but then I avoid those for body-to-body sextant checks
    as refraction in general becomes problematic.
    
    This has little to no significance on the water, but may be of concern when
    doing star-to-star or body-to-body distances--especially when and unnamed
    person is disappointed if the measurements are 0!3 off over a 106d range.
    (This despite his position that station pressure and temperature adjustment
    are a waste of energy.) 
    
    I had wondered about your highly-informed opinion on the best method for Hc
    to Ho. Pretty well answered by, "If you have the table, you should *never*
    use those fitted equations."
    
    Bill
    
    
    
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