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    Re: Error in H.O. 229 Introduction/Explanation?
    From: Sean C
    Date: 2013 Apr 19, 08:53 -0700

    Greg,

    You wrote:
    "The Pub 229 tables for some reason uses the north hemisphere azimuth rules for Z when Hc becomes a negative altitude so for your example LHA 240 Lat 45 S Dec 5 S Z = Zn."

    This statement is true, and would be the correct procedure. And this is what the rules printed on each opening of the table would have you do. However, if you read the introduction carefully, you will see that the author is, in fact, not using these rules. He/she is using the South hemisphere rules.

    You continued:
    "When using the NGA 229 calculator the Z rules don't change when the altitude becomes negative (see attached pic 175)."

    This is also true. And, IMHO, in error. Which leads me to believe that whoever coded the calculator used the introduction as a guide.

    Further, none of this explains why, in the second part of the paragraph, when the body is ABOVE the horizon, the author again uses the wrong rules (this time North hemisphere for a body above the horizon in the South) and arrives at the wrong azimuth.

    Please, anyone correct me if I am wrong.

    -Sean C.
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