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    Re: 'The Complete On-Board Celestial Navigator' book
    From: Marcelo Martinez Borja
    Date: 2003 Mar 30, 15:24 -0500

    thanks
    
    
    
    
    
    
    >From: Peter Fogg 
    >Reply-To: Navigation Mailing List 
    >To: NAVIGATION-L{at}LISTSERV.WEBKAHUNA.COM
    >Subject: Re: 'The Complete On-Board Celestial Navigator' book
    >Date: Sun, 30 Mar 2003 06:56:32 +1000
    >
    >('The dog ate my homework' - the electronic gremlins have consigned my
    >original message to some black hole, its a great mystery, so this is
    >another attempt ..)
    >
    >Gerard Mittelstaedt wrote:
    >
    > > Hi,
    > >  I ... found
    > > The Complete On-Board Celestial Navigator
    > > by George G Bennett   isbn = 0-07-139657-8
    > > listed on Amazon.com
    > >
    > > The book is organized in 11 chapters, that can
    > > be logically organized into sections on
    > > - How to
    > > - Almanac data, including
    > >   Stars & Aries, Sun & planets, Moon
    > > - "planning observations"
    > > - sextant corrections
    > > - the Marcq St.Hilaire Method -
    > > and various tables and forms.
    >
    >Apart from what you have mentioned, it also has:
    >
    >  * 'Prediction and Identification' tables for stars and also Sun, Moon
    >and planets,
    >  * Graphs for finding the Local Apparent Time of sunrise and sunset,
    >  * The same thing for LAT of morning and evening Civil Twilight,
    >  * 3 methods for calculating Azimuth,
    >  * Star charts for the southern and northern sky
    >  * An explanation of using Amplitude for checking a compass
    >  * Latitude using Polaris
    >  * Latitude using noon Sun (called 'Meridian Observations')
    >  * A page titled 'Calculator Interpolation'
    >  * 'Change of Altitude in 5 Minutes of Time'
    >  * 'Sextant Altitude Observations' these last two are the method and
    >blank form for plotting a series of observations against the body's
    >apparent rise or fall over 5 minutes. A wonderful method to plot a
    >series of sights graphically, can indicate better data than any of the
    >individual sights.
    >
    >As always, there is an explanation and a worked out example to follow.
    >
    > >
    > > The Almanac section of "The Complete..." seems
    > > to be abbreviated, and probably needs a lot of
    > > interpolation for use.
    >
    >In the almanac section, first comes the:
    >
    >  'GHA for Aries' for each day, incl. time of day correction.
    >Opposite each page is an 'Index of Bright Stars' with SHA and Dec, the
    >Dip correction and the altitude corr., everything you need here is on
    >the two facing pages.
    >
    >'Sun and Planets' section is similar, GHA and Dec listed for each day,
    >the 'v' and 'd' corrections and interpolations are found at the end of
    >these pages.
    >
    >The Moon has the GHA and Dec listed for each 6 hours of GMT, again the
    >interpolation pages for 'v' and 'd' and altitude. corr. HP etc are at
    >the end of this section. You can either look up the corrections and
    >interpolations or use a calculator to work them out more accurately, its
    >all there.
    >
    >As for abbreviated, the data in the almanac and also the sight reduction
    >method is presented to the nearest minute of arc. This enables it all to
    >fit into such a compact format and does simplify things greatly.
    >Recently on this list there was a discussion of how accurate CN could
    >be. For a surveyor using a theodolite on a tripod that can be very
    >accurate indeed, but for a navigator on a small boat the greatest
    >impediment to accuracy is likely to be the boat's movement. Being able
    >to work out an intercept to the nearest nautical mile, using just the
    >one book (and its photocopied forms) fairly simply and quickly, needing
    >only simple addition, seems to be the book's aim.
    >
    >The sight reduction method uses a DR, a position in degrees and minutes
    >of arc. Compared to a method that uses an assumed position to the
    >nearest whole degrees the intercepts tend to be shorter and thus
    >indicate more accurately the position. With this method, should the DR
    >turn out to be a long way from the fix, the sight reduction process can
    >be repeated using the fix as an improved DR and the new intercepts
    >should be much shorter and thus more accurate. Only simple addition is
    >needed to process the data through the sight reduction method, and the
    >form is provided. It starts with the local day and date and finishes
    >with the intercept and azimuth. Along the way it has handy reminders
    >where they are helpful (+Slow, -Fast and +West, -East for example) and
    >as well the book comes with a page of step by step instructions that
    >walk you through the process of sight reduction, and a suggestion that
    >you photocopy this page, put the page of time/degree conversions on the
    >other side, and cover them with plastic. This sheet then becomes a handy
    >bookmark and is often referred to.
    >
    >I am not aware of any other book that compares with this one, that wraps
    >up everything the navigator could need for practical CN (except the
    >sextant!) in the one compact package. It can even be used as a textbook,
    >as in 6 short chapters it goes through the theory and method using
    >worked out examples at each stage. It does assume a basic understanding
    >of latitude and longitude and plotting; let's say the skills of coastal
    >navigation as a starting point. It lies open flat, much appreciated
    >on-board (I once was silly enough to buy a paperback Nautical Almanac,
    >it drove me mad trying to extract data from it - I never had enough
    >hands!) a small point but typical, I think, of how well this book has
    >been planned for practical use.
    >
    > >
    > > The price was modest (just under $20.00 US),
    > > and I bought it.
    >
    >Half your luck (says me sourly) books are much more expensive here. Just
    >as well I think its worth every penny. Good luck with it, Gerard and
    >everyone else who has it, let us know how you find it with a little more
    >familiarity and practice.
    >
    >
    >Glossary
    >
    >CN    Celestial Navigation
    >GHA  Greenwich Hour angle
    >LAT    Local Apparent Time
    >SHA   Sidereal Hour Angle
    >Dec    Declination
    >DR     Deduced Reckoning; a calculated position advanced from a previous
    >fix.
    >fix       Postion established by CN or some other method
    
    
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