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    Re: H.O. 218 Vs. H.O. 249
    From: Stan K
    Date: 2015 Nov 7, 17:35 -0500
    Ah ha!  The difference is because the computed altitudes include the refraction correction (for a 5,000 foot flight altitude, but virtually the same as at sea level), according to Gary LaPook.  Thanks, Gary.  Nice having the archives.


    -----Original Message-----
    From: slk1000 <slk1000---.com>
    To: navlist <navlist@fer3.com>
    Cc: slk1000 <slk1000---.com>
    Sent: Sat, Nov 7, 2015 5:10 pm
    Subject: H.O. 218 vs. H.O. 249

    A short time ago I mentioned that I had a copy of Volume J of H.O. 218, but I had not done anything with it yet.  Well,  I started looking at it, and I am confused.

    218 is similar to 249.  I am working with Part 2 of 218, which corresponds to Volumes 2 and 3 of 249, the ones that do not refer to particular stars.  I am finding what I consider significant differences between 218 and 249.  For example:

    Declination 1ºN
    Latitude 40ºN
    LHA 76º

    For 249 and any method other than 218 I have tried, this gives an altitude of 11º20'.  218 gives 11º24'.  The values of d and azimuth agree, it is just the altitude that is off.  Most other sets of inputs I have tried disagree by one to four minutes of altitude, with an occasional one agreeing.

    The volume I have is dated 1941.  Is it possible that this edition has issues but later editions have different numbers?  Or do all editions have issues?  Or do I have issues?

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