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    Re: Sight reduction formulae
    From: Stan K
    Date: 2011 Dec 1, 14:51 -0500
    Randall,

    In my previous e-mail I should have added that
    1) in the sin formula, that sign is always +
    2) in the cos formula, that sign is always -, but the formula is missing parentheses
    cos Az * =  (sin dec +/- (sin Hc x sin DR lat)) divided by (cos Hc x cos DR lat)

    Stan


    -----Original Message-----
    From: Randall.F.Morrow <Randall.F.Morrow@kp.org>
    To: NavList <NavList@fer3.com>
    Sent: Thu, Dec 1, 2011 2:37 pm
    Subject: [NavList] Sight reduction formulae


       I'm trying to do sight reductions by calculator but I'm having trouble with the sign(s).     On example I have found is below but I have seen others in which the sign(s) do not change with same versus contrary latitude and declination.    Is this correct?   (I don't remember where I found this)
    Thanks, Randy

    sin Hc = (cos LHA x cos DR lat x cos dec)  + or - (sin DR lat x sin dec)
    Note: use + if lat and dec are same names.
    cos Az * =  sin dec +/- (sin Hc x sin DR lat) divided by (cos Hc x cos DR lat)
    Note: use + when lat  and dec are of opposite names.
    * Remember Az is the azimuth angle. To get Zn (Azimuth) apply the rules:
    Northern Lat:  LHA > 180 deg. Azimuth = Azimuth Angle.   LHA < 180 deg. Zn = 360 - Az
    Southern Lat.  LHA > 180 deg. Zn = 180 deg. - Az.   LHA< 180 deg. Zn = 180 + Az  




    Randall F Morrow PT
    Kern County - Bakersfield


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