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    Re: Round Two: with a bonus ex-meridian
    From: Peter Hakel
    Date: 2013 Mar 8, 14:09 -0800
    The many-body fix at 19:00:00 local time comes out right on the money (see attached sights.xls and many_body_fix.xls):

    Lat: N 20d 38.6'
    Lon: E 120d 48.9'

    For the Achernar ex-meridian, I first advance the above position by 4 minutes and 1 second ( = 0.0669 hours, using time.xls and dr.xls) to the instant when Achernar was observed:

    Lat: N 20d 39.2'
    Lon: E 120d 49.7'

    This longitude has the "GHA equivalent" of 239d 10.3'.  Achernar transited that meridian at UT = 09:50:53 (aries_stars.xls), whereas its observation was made 13 minutes and 8 seconds later (time.xls).

    From ex_meridian.xls I get:
    Lat: N 20d 39.3'
    only 0.1' from the latitude of the DR-advanced many-body fix.

    Peter Hakel

    From: Antoine Couëtte <antoine.m.couette{at}club-internet.fr>
    To: pmh099---.com
    Sent: Friday, March 8, 2013 12:11 PM
    Subject: [NavList] Re: Round Two: with a bonus ex-meridian

    RE : NavList Post # 22641
    Let us change things up a bit with this round of stars. 5 bodies, with one that can be reduced as an ex-meridian of an upper transit (hint it's Achernar).
    We are going a bit faster now so you might want to advance the later sights for accuracy.
    Ship data:
    Date: 16 January 2013
    ZD -9 (note change)
    Crs: 049 Deg
    Spd 14.6 knots
    Height of eye: 83 ft
    Index error: 0.9' on the arc
    Temp 72 deg F
    Pressure 1016 mB.
    GPS fix at 1900-00 is Lat 20-38.6'N Long 120-48.9'E
    Star Data:
    Capella: 1900-27 Hs 40-40.2'
    Aldebaran: 1901-12 Hs 50-13.3'
    Rigel: 1902-27 Hs 32-03.8'
    Achernar: 1904-01 Hs 12-21.2'
    Fomalhaut: 1905-32 Hs 24-43.2'
    Fix a celestial fix at 1900 LT, "error" from the GPS fix, and standard deviation of the intercepts.
    Hello Jeremy,

    From your GPS Position used as DR, and updated for each observation time, I get:
    CAPELLA -0.5NM/046°4
    ALDEBARAN +0.4NM/088°6
    RIGEL -0.4NM/114°4
    ACHERNAR -0.1NM/181°8
    FOMALHAUT _0.1NM/221°3
    Sdev (i.e. LOP's dispersion) = 0.3 NM
    Position in Bearing 298° from DR and at distance of 0.1 NM
    Lesson learnt : What's the use of the GPS if you can get a Celnav position within 0.1 NM of true Position ?
    Attaboy ! Well done, once again, Skipper !
    Antoine M. "Kermit" Couëtte
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    File: 122735.sights.xlsx
    File: 122735.many_body_fix.xls
    File: 122735.time.xls
    File: 122735.dr.xls
    File: 122735.aries_stars.xls
    File: 122735.ex_meridian.xls
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