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    Re: "The complete on-board celestial navigator" by Bennett
    From: Peter Fogg
    Date: 2009 Nov 2, 13:33 +1100
    Hey rcallum
     
    The author can be justifiably pleased that you use the book to such an extent that you have gone to so much effort to improve its shortcomings, as you perceive them.  I have also used the book extensively, although without being irritated by the layout of the tables.  Does your edition include formulas?  Their use with a calculator or a speadsheet eliminates looking up tables.
     
    One of the book's strengths, to my mind, is the provision to the user of multiple methodologies to achieve the same outcome, and the different ways provided of calculating azimuth (including direct calculation via different formulas) is but one example of this.  It is unfortunate if this profusion of possible methods proves confusing, although I guess that the user soon chooses a method to favour, as you have done.
     
    Shall pass on your comments to the author for consideration when preparing the next edition, and thank you on his behalf for them.

    On Mon, Nov 2, 2009 at 12:17 PM, <rcallumfree---.com> wrote:

    I have used this book extensively and find a number of shortcomings.

    The table lookup process is error prone and slow due to top/bottom access to the tables, the unnecessary combination of the Lat Dec with the sum res table and the total absence of any indexing mechanism. I have resolved this by recreating and reprinting the tables. I use a separate Lat Dec Table, 6 pages tab indexed by degrees a double facing page covering 30 degrees. The sum res table is extended to 12 pages each double page covering 15 degrees and is tab indexed by degree sum and res making getting to the right page instantly a snap. The remaining 6 pages cover LHA 90 to 180 indexed by degrees. All of these are double facing pages giving the maximum coverage on one opening. I have eliminated bottom access with two additional computation steps, if LHA is greater than 180 then tableLHA=359.60-LHA and by finaly extracting Z from the top of the res table alt=89.60-Z. Despite the additional steps I have found this is MUCH faster and less stressful to use despite an extra 4 pages of tables.

    As has been already discussed the inclusion of several different methods of azimuth determination is confusing to the novice. My personal preference is for Weir diagrams. The result is unambiguous and can be transfered directly from diagram to plotting sheet using a Bretton plotter. The diagrams provide in the book are not big enough or detailed enough although the idea of splitting them into four separate diagrams is a good one.

    Despite these problems the book is a good minimalist solution to get you home astronav. It could be much improved by the suggestions above even if we had to cut out the tabs ourselves. Please International Marine for the 2011-2015 edition.

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