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>From: Peter Fogg 
>Reply-To: Navigation Mailing List 
>To: NAVIGATION-L@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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