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    Re: Sight Reduction via Daily Pages in NA v.NA Concise Sight Reduction Tables
    From: Hewitt Schlereth
    Date: 2011 Jan 9, 10:56 -0400

    Alan -
    I'm curious about what you have been doing so far to determine the
    accuracy of your sights?
    On 1/9/11, Gary LaPook  wrote:
    > Here is my evaluation of several methods of sight reduction.
    > I learned celestial from Mixter, fourth edition, and this book included
    > a complete reprint of H.O. 211 so this is the first sight reduction
    > method that I learned. I soon bought a set of H.O. 214 and never looked
    > back, H.O. 211 is my least favorite method of sight reduction. Of the
    > _tabular_ methods I much prefer Dreisonstok at this point. (But I am
    > real partial to my Bygrave slide rule.) When my eyes were younger I
    > preferred the Weems Line Of Position Book but I have greater difficulty
    > now using the Rust diagram. Apparently others complained about this
    > because Weems includes a mathematical solution for azimuth in addition
    > to the Rust diagram in the 1944 edition of his book. He made some other
    > changes at the same time. He changed the arrangement of
    >  table A so now
    > each page is entered by latitude not by LHA which adds convenience for
    > working a number of sights from the same assumed latitude similar to the
    > convenience of H.O. 249, H.O. 218  and of H.O. 214 compared to the
    > _inconvenience_ of H.O. 229 (I still don't know why they changed the
    > arrangement and ruined a good thing!) He also changed the size of the
    > book from a handy 10 by 6 inches to a much larger 14 by 8 1/2 inches,
    > not so handy but it does make the printing larger.
    > So comparing the various standard methods of paper based sight reduction
    > the Haversine- Cosine method takes the most work. The Sine -cosine
    > method is a little bit less work but there is the problem with logs of
    > negative values of cosine for LHA. Although this method can work with
    > some cases, since it cannot be used in all cases it just makes a
    > navigator's life more difficult to learn both of these methods. (It is
    > probably the best method to use with a calculator, however.)
    > I am attaching a list of keystrokes to use in solving this
    > �with a calculator. (Note, this corrects a typo in my original
    > posting of the keystrokes so the previous version should not
    > be used.)
    > All the short tabular methods are more convenient than the previous
    > two.Of the short methods H.O. 211 takes the most work (although it does
    > allow working from the D.R. but this normally doesn't make any
    > difference in practical navigation) followed by H.O 208 and the shortest
    > solution is the Weems Line Of Position Book.
    > The inspection tables, H.O 214, H.O. 218, and H.O. 249 have the same
    > arrangement of tables and are equally convenient. H.O. 249 volume 1 is
    > especially good when working a round of star sights as you don't need to
    > compute individual LHAs so for this use it is better than the other
    > tables. H.O 214 includes the necessary factors to allow working from a
    > D.R. but you can also calculate these factors for H.O. 218 and H.O 249
    > if you need to do this, such as for practice sights from a known
    > location. These tables are only
    >  slightly faster than the Weems book. All
    > the inspection tables take up more space on the shelf than the short tables.
    > H.O 229 is not as convenient as the other inspection tables and requires
    > more interpolations. However these  tables might provide slightly
    > greater accuracy for high altitude sights but this probably makes no
    > difference for practical
    >  navigation.
    > ----------------------------------
    > These are links to examples of sight reduction using different methods
    > using data provided by Chichester all from the archives for December 2008.
    > http://www.fer3.com/arc/m2.aspx?i=106696&y=200812
    > http://www.fer3.com/arc/m2.aspx?i=106697&y=200812
    > http://www.fer3.com/arc/m2.aspx?i=106700&y=200812
    > http://www.fer3.com/arc/m2.aspx?i=106702&y=200812
    > http://www.fer3.com/arc/m2.aspx?i=106705&y=200812
    > http://www.fer3.com/arc/m2.aspx?i=106707&y=200812
    > http://www.fer3.com/arc/m2.aspx?i=106708&y=200812
    > http://www.fer3.com/arc/m2.aspx?i=106720&y=200812
    > http://www.fer3.com/arc/m2.aspx?i=106721&y=200812
    > http://www.fer3.com/arc/m2.aspx?i=106744&y=200812
    > http://www.fer3.com/arc/m2.aspx?i=106745&y=200812
    > http://www.fer3.com/arc/m2.aspx?i=106747&y=200812
    > http://www.fer3.com/arc/m2.aspx?i=106760&y=200812
    > gl
    > --- On Sat, 1/8/11, Alan  wrote:
    > From: Alan 
    > Subject: [NavList] Sight Reduction via Daily Pages in NA v.NA Concise Sight
    > Reduction Tables
    > To: NavList@fer3.com
    > Date: Saturday, January 8, 2011, 9:11 PM
    > Given that my efforts at Celestial Navigation are limited to, and unlikely
    > to progress beyond standing on the beach, when I can get there, shooting
    > whatever happens to be in view, day time and or evenings, it doesn't make a
    > whole lot of difference, however I learned to do sight reduction using the
    > NA Daily Pages and the Law of Cosines, which strike me as a simple to use,
    > direct, straight forward approach to sight reduction.Lately, I have begun to
    > delve into use of the NA Concise Tables, a Power Squadron Nav course I'm
    > taking requires reduction of sextant sights by both  methods. I understand
    > that the Concise Tables Method are supposedly simpler, easier to use.Perhaps
    > they are, doing the Law of Cosines absent a calculator, using  log tables
    > would be tedious as hell, however as to the Concise Tables being
    > "simpler/easier to use", I beg to differ, for it seems that the Concise
    > Tables involve endless messing about with and or the massaging of numbers,
    > which
    >  one doesn't have to do using the Law of Cosines. Of course, I might be
    > missing a salient point perhaps more than one here, for instance what
    > happens if one's calculator craps out. Of course, with the Concise Tables,
    > one would be out of luck if they lost their NA over the side. Seriously
    > though, is there something basic or obvious here that escapes me?In
    > appreciation of any input or clarification
    > offered.Alan----------------------------------------------------------------
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