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    Re: Dutton's Book Best on CelNav
    From: Courtney Thomas
    Date: 2003 Sep 13, 14:37 -0500

    Bill,
    
    Frankly, I didn't realize my comments were going to the group. I truly
    thought it was a bilateral discussion between Phil and I. I must monitor
    the To: entry on my browser.
    
    Anyhow, I'm gratified that you concur. I truly sympathize with anyone
    trying to comprehend celnav without a copy of Dutton. They won't make it
    unless they are a helluva lot smarter than several centuries of
    mathematicians and navigators.
    
    NavigationLite won't cut it.
    
    Courtney
    
    
    
    William Allen wrote:
    
    > Courtney,
    >
    > I agree completely with your assessment of why celnav is viewed as
    > difficult and I also believe that Dutton's is the best of the texts.  As
    > far as I know, it has not been updated or reprinted since the mid-80s
    > (which in no way diminishes its value for learning celnav).  When I was
    > learning the basics of celnav, I poured through its chapters and
    > examples over and over.  I also studied a number of other books, which
    > did not give the same depth of treatment and always left me a bit
    > frustrated.
    >
    > But I am curious why it has not continued in current production?
    >
    > Bill Allen
    >
    > -----Original Message-----
    > From: Navigation Mailing List
    > [mailto:NAVIGATION-L{at}LISTSERV.WEBKAHUNA.COM] On Behalf Of Courtney
    > Thomas
    > Sent: Saturday, September 13, 2003 7:46 AM
    > To: NAVIGATION-L{at}LISTSERV.WEBKAHUNA.COM
    > Subject: Re: Fwd: Principles and Being Practical
    >
    > Phil,
    >
    > I haven't received Powell's book yet, but after rambling around in a
    > number of books that supposedly are able to put it over, I've decided
    > that the only one I've seen that actually does is......... "Dutton".
    > Very Euclidean in approach.
    >
    > He not only gives examples for those only interested in the mechanics,
    > but does it well and as thoroughly as one wishes to delve. He also lays
    > the entire abstract layer out, if full comprehension is sought.
    >
    > I think this is why celnav is regarded as difficult, i.e. a proper
    > laying down of the basis is not done, hence a superficial, if any at all
    > perception is absorbed. Hence, all the mistakes in trying to compute
    > anything, since there's no real grasp, hence a disorientation and
    > slippery feel to it all. Like everything, you are not going to get out
    > more than you put in and what you put in needs to be thorough and
    > complete, else a lot of frustration and ultimately failure ensues. The
    > U.S. Navy, WWII vintage, got it right.
    >
    > I think all the rest are like the new books that supposedly teach
    > history or reading for kids. Big on appearance and little substance.
    >
    > I'd recommend everyone quit wasting money and time and simply go to any
    > online used book site and get a copy of Dutton for $5 and be done with
    > it.
    >
    > I value mine so much [7th Edition] that I had it's hardcover rebound
    > anew.
    >
    > Cordially,
    > Courtney
    >
    >
    >
    > HGWorks - Phil Guerra wrote:
    >
    >
    >>Courtney,
    >>
    >>Susan Powell's book includes HO229 fragments needed to do the
    >>
    > exercises, and
    >
    >>the US Navy site, I gave in the last message has some links to the
    >>
    > different
    >
    >>volumes of the HO 229, and HO249, so either way would work.  Have you
    >>
    > seen
    >
    >>the Susan Powell book?
    >>
    >>Phil
    >>----- Original Message -----
    >>From: "Courtney Thomas" 
    >>To: 
    >>Sent: Thursday, September 11, 2003 8:06 PM
    >>Subject: Re: Fwd: Principles and Being Practical
    >>
    >>
    >>
    >>
    >>>Thanks again Phil.
    >>>
    >>>I have the HO 249 set. I just wondered if Susan Howell's book would
    >>>apply equally well to 249 as 229.
    >>>
    >>>Cordially,
    >>>Courtney
    >>>
    >>>
    >>>
    >>>HGWorks - Phil Guerra wrote:
    >>>
    >>>
    >>>
    >>>>Basically,
    >>>>
    >>>>The methods are closely related, being different in the tables used
    >>>>
    > to
    >
    >>>>acquire the data in the sight reduction, and some technique
    >>>>
    > variations.
    >
    >>The
    >>
    >>
    >>>>HO 249 is a 3 volume set originally designed for use by aviation
    >>>>
    >>>>
    >>navigators,
    >>
    >>
    >>>>and the HO 229 is an six volume set, with far more solutions.
    >>>>
    > However,
    >
    >>the
    >>
    >>
    >>>>HO229 is costly and probably not the most widely used by other than
    >>>>
    > the
    >
    >>most
    >>
    >>
    >>>>serious navigators.  That's why short tables, such as Bayless, and
    >>>>
    >>>>
    >>Ageton
    >>
    >>
    >>>>are still used, though not as much with the advent of cheap
    >>>>
    > navigation
    >
    >>>>computers and GPS.
    >>>>
    >>>>Really, though I think you can adapt from either, it just takes
    >>>>
    > finding
    >
    >>your
    >>
    >>
    >>>>way through one of the methods and getting a good feel for it.
    >>>>
    > Again,
    >
    >>I'm
    >>
    >>
    >>>>sure others could help you assess which one is right for you.  The
    >>>>
    >>>>
    >>precision
    >>
    >>
    >>>>of the HO 229 is probably more than you need on a regular basis, but
    >>>>
    > you
    >
    >>>>never know what you miss until you don't have it.  Check out the US
    >>>>
    > Navy
    >
    >>>>site to read more about it, and take a look at their great
    >>>>
    > documentation
    >
    >>and
    >>
    >>
    >>>>computer utilities at this site:
    >>>>http://aa.usno.navy.mil/publications/
    >>>>
    >>>>Still if you need to move quickly, you may need to contact a Sailing
    >>>>
    > /
    >
    >>>>Navigation School.  My desk rarely moves, so I've got a little more
    >>>>
    > time
    >
    >>to
    >>
    >>
    >>>>play with than you, I suspect.
    >>>>
    >>>>Take care,
    >>>>
    >>>>Phil
    >>>>
    >>>>
    >>>>----- Original Message -----
    >>>>From: "Courtney Thomas" 
    >>>>To: 
    >>>>Sent: Tuesday, September 09, 2003 5:22 AM
    >>>>Subject: Re: Fwd: Principles and Being Practical
    >>>>
    >>>>
    >>>>
    >>>>
    >>>>
    >>>>>Phil,
    >>>>>
    >>>>>Thank you for the book information.
    >>>>>
    >>>>>What is the difference between HO 249 and HO 229 techniques ?
    >>>>>
    >>>>>Cordially,
    >>>>>Courtney
    >>>>>
    >>>>>
    >>>>>
    >>>>>HGWorks - Phil Guerra wrote:
    >>>>>
    >>>>>
    >>>>>
    >>>>>
    >>>>>>Sorry for the tardy reply.  Yes, I've got Mary Blewitt's book, as
    >>>>>>
    > well,
    >
    >>>>>>although, I've misplaced it.  I found it to be a really good
    >>>>>>
    > reference,
    >
    >>>>>>
    >>>>and
    >>>>
    >>>>
    >>>>
    >>>>>>it's compact size made it easy to take to work for reading on my
    >>>>>>
    >>>>>>
    >>breaks.
    >>
    >>
    >>>>If
    >>>>
    >>>>
    >>>>
    >>>>>>I remember correctly, she uses the H.O.249 to do sight reductions.
    >>>>>>
    >>>>>>
    >>Other
    >>
    >>
    >>>>>>methods are given some mention, but not really examined.
    >>>>>>
    >>>>>>The book I really worked through was Susan Powell's Practical
    >>>>>>
    > Celestial
    >
    >>>>>>Navigation.   It's more like a workbook giving lots of examples and
    >>>>>>solutions.  She uses the H.O. 229 for her sight reduction work.  I
    >>>>>>
    >>>>>>
    >>think,
    >>
    >>
    >>>>>>the method you use depends on your specific needs.  What's most
    >>>>>>
    >>>>>>
    >>important
    >>
    >>
    >>>>is
    >>>>
    >>>>
    >>>>
    >>>>>>that you know your method down pat, and have a backup method or
    >>>>>>
    > two.
    >
    >>>>>>I know many of the list's group could tell you more, I've no real
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>experience
    >>>>
    >>>>
    >>>>
    >>>>>>in actual on-board CN.  I'm just in awe and admire all who are able
    >>>>>>
    > to
    >
    >>do
    >>
    >>
    >>>>>>it.  I enjoy the mechanics of the process of CN because it
    >>>>>>
    > emcompasses
    >
    >>so
    >>
    >>
    >>>>>>many of my interests into an area that uses them all.  Good luck to
    >>>>>>
    >>>>>>
    >>you.
    >>
    >>
    >>>>>>Phil Guerra
    >>>>>>www.hgworks.com
    >>>>>>----- Original Message -----
    >>>>>>From: "Courtney Thomas" 
    >>>>>>To: 
    >>>>>>Sent: Sunday, September 07, 2003 4:29 PM
    >>>>>>Subject: Re: Fwd: Principles and Being Practical
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>Phil,
    >>>>>>>
    >>>>>>>Thanks so much for the fulsome reply.
    >>>>>>>
    >>>>>>>I am a non-armchair sailor and am trying to find the best, i.e.
    >>>>>>>
    >>>>>>>
    >>easiest
    >>
    >>
    >>>>>>>that meets real world navigational needs, CN technique rather than
    >>>>>>>
    > a
    >
    >>>>>>>more abstract interest but thank goodness for such.
    >>>>>>>
    >>>>>>>I suspect Newton would've probably been a poor farmer but
    >>>>>>>
    > gratefully
    >
    >>so.
    >>
    >>
    >>>>>>>For now I just don't want to waste time/energy learning one
    >>>>>>>
    > technique
    >
    >>to
    >>
    >>
    >>>>>>>later learn that it was not the most suitable.
    >>>>>>>
    >>>>>>>It's not that it is intrinsically uninteresting it's that my
    >>>>>>>
    > agenda is
    >
    >>>>>>>reversed, at this time.
    >>>>>>>
    >>>>>>>Incidentally, are you familiar with Mary Blewitt's book ? If yes,
    >>>>>>>
    > what
    >
    >>>>>>>do you think of it ?
    >>>>>>>
    >>>>>>>Cordially,
    >>>>>>>Courtney
    >>>>>>>
    >>>>>>>
    >>>>>>>
    >>>>>>>HGWorks - Phil Guerra wrote:
    >>>>>>>
    >>>>>>>
    >>>>>>>
    >>>>>>>
    >>>>>>>
    >>>>>>>
    >>>>>>>>The Ageton method is not discussed in Bennett's book.  It is
    >>>>>>>>
    > really a
    >
    >>>>>>>>compact treatment of the subject designed for use on-board.  As
    >>>>>>>>
    > far
    >
    >>as
    >>
    >>
    >>>>>>>>
    >>>>>>the
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>best explanation of the method, I never really found anything
    >>>>>>>>
    > more
    >
    >>than
    >>
    >>
    >>>>>>>>
    >>>>>>his
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>book, "Manual of Celestial Navigation" in print.  I found the
    >>>>>>>>
    > book by
    >
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>chance
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>in a used book store, but have seen it offered on Ebay for around
    >>>>>>>>
    > an
    >
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>average
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>price of 10-20 dollars (US).  Unfortunately, the book is not
    >>>>>>>>
    > really a
    >
    >>>>>>>>'teaching guide' but probably was used to supplement classroom
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>instruction.
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>Another, offshoot of the method was put forward by Allan E.
    >>>>>>>>
    > Bayless,
    >
    >>>>>>>>"Compact Sight Reduction Table", again using a slight
    >>>>>>>>
    > modification of
    >
    >>>>>>>>Ageton's method.  This book is out of print as well, and I found
    >>>>>>>>
    > a
    >
    >>copy
    >>
    >>
    >>>>>>>>
    >>>>>>on
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>Ebay.
    >>>>>>>>
    >>>>>>>>My expanding CN library includes, Bowditch, Dutton's Navigation &
    >>>>>>>>
    >>>>>>>>
    >>>>>>Piloting,
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>which all refer to the method, but really do not give it much
    >>>>>>>>
    >>>>>>>>
    >>clarity,
    >>
    >>
    >>>>>>>>
    >>>>>>at
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>least for me coming in as a novice.  This lead me to ask
    >>>>>>>>
    > questions on
    >
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>this
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>list about it.  I did find a good description on a referenced web
    >>>>>>>>
    >>>>>>>>
    >>site
    >>
    >>
    >>>>>>>>http://home.t-online.de/home/h.umland/page3.htm, by Henning
    >>>>>>>>
    > Umland,
    >
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>which
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>cleared up most of the questions regarding how to use it, as his
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>authored,
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>"The Ageton Tables", gives some good description of the method,
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>examples,
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>and solutions.  Umland did expand the method a bit by providing a
    >>>>>>>>
    > new
    >
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>set of
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>tables to give it more accuracy.  The site is a great starting
    >>>>>>>>
    > point
    >
    >>>>>>>>information regarding CN in general, and he has a lot of very
    >>>>>>>>
    > useful
    >
    >>CN
    >>
    >>
    >>>>>>>>links.   After going through Umland's article, I was able to go
    >>>>>>>>
    > back
    >
    >>to
    >>
    >>
    >>>>>>>>
    >>>>>>the
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>Bowditch and Dutton books and understand the terse descriptions
    >>>>>>>>
    > and
    >
    >>>>>>>>
    >>>>work
    >>>>
    >>>>
    >>>>
    >>>>>>the
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>examples yielded the solutions.
    >>>>>>>>
    >>>>>>>>I've begun work on using the information gleamed from all of my
    >>>>>>>>
    >>>>>>>>
    >>sources
    >>
    >>
    >>>>>>>>
    >>>>>>to
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>produce a web site to teach the method, but it's stalled at
    >>>>>>>>
    > present
    >
    >>due
    >>
    >>
    >>>>>>>>
    >>>>>>to
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>other responsibilities.  However, if you need help understanding
    >>>>>>>>
    > it,
    >
    >>>>>>>>
    >>>>let
    >>>>
    >>>>
    >>>>
    >>>>>>me
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>know via my existing web site www.hgworks.com using the Contact
    >>>>>>>>
    > Us
    >
    >>>>>>>>
    >>>>page.
    >>>>
    >>>>
    >>>>
    >>>>>>I
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>found that building the web application to use Ageton gave great
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>accuracy
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>with the mathematical model, and using the table values gave it
    >>>>>>>>
    > such
    >
    >>>>>>>>accuracy that it was, I believe in use for over 30 years, before
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>falling
    >>>>
    >>>>
    >>>>
    >>>>>>out
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>of favor, due to technological advancements.  There are questions
    >>>>>>>>
    > of
    >
    >>>>>>>>accuracy in Azimuth calculation, and it is documented.
    >>>>>>>>
    >>>>>>>>Although, I'm a 'deskbound navigator', others who I've come into
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>contact
    >>>>
    >>>>
    >>>>
    >>>>>>>>with on this list, indicate that the methods and books are still
    >>>>>>>>
    > used
    >
    >>>>>>>>on-board, which is testament to the value of the work done.
    >>>>>>>>
    >>>>>>>>Hope this helps,
    >>>>>>>>
    >>>>>>>>Phil Guerra
    >>>>>>>>www.hgworks.com
    >>>>>>>>
    >>>>>>>>----- Original Message -----
    >>>>>>>>From: "Courtney Thomas" 
    >>>>>>>>To: 
    >>>>>>>>Sent: Sunday, September 07, 2003 4:15 AM
    >>>>>>>>Subject: Re: Fwd: Principles and Being Practical
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>Is Ageton's method described in Bennett's book ? If not, where
    >>>>>>>>>
    > is
    >
    >>the
    >>
    >>
    >>>>>>>>>best exegesis of it, please ?
    >>>>>>>>>
    >>>>>>>>>Thank you.
    >>>>>>>>>
    >>>>>>>>>Dr. Geoffrey Kolbe wrote:
    >>>>>>>>>
    >>>>>>>>>
    >>>>>>>>>
    >>>>>>>>>
    >>>>>>>>>
    >>>>>>>>>
    >>>>>>>>>
    >>>>>>>>>>George Huxtable has pointed up a potential problem with the
    >>>>>>>>>>
    > azimuth
    >
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>tables
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>>in George Bennett's book "The Complete On-board Celestial
    >>>>>>>>>>
    >>>>>>>>>>
    >>Navigator".
    >>
    >>
    >>>>>>>>>>
    >>>>>>He
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>>>has shown that there can be errors in computed azimuth of (at
    >>>>>>>>>>
    >>>>>>>>>>
    >>least)
    >>
    >>
    >>>>15
    >>>>
    >>>>
    >>>>
    >>>>>>>>>>degrees where the celestial body is that sort of distance away
    >>>>>>>>>>
    > from
    >
    >>>>>>>>>>
    >>>>the
    >>>>
    >>>>
    >>>>
    >>>>>>>>>>prime vertical.
    >>>>>>>>>>
    >>>>>>>>>>Peter Fogg tells us that this is "nit-picking" and that in any
    >>>>>>>>>>
    >>>>>>>>>>
    >>case,
    >>
    >>
    >>>>>>>>>>
    >>>>>>the
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>>>book tells us that, "In extreme cases the table should be
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>interpolated
    >>>>
    >>>>
    >>>>
    >>>>>>>>when
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>>observations have been made in the vicinity of the prime
    >>>>>>>>>>
    > vertical."
    >
    >>>>>>>>>>I do not have the second edition, only the 1999-2003 edition
    >>>>>>>>>>
    > where
    >
    >>>>>>>>>>
    >>>>this
    >>>>
    >>>>
    >>>>
    >>>>>>>>>>phrase is not present. Perhaps Peter can tell us just what
    >>>>>>>>>>
    >>>>>>>>>>
    >>"extreme"
    >>
    >>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>means
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>>in this context? When do we know we are in an extreme case?
    >>>>>>>>>>
    > George
    >
    >>>>>>>>>>
    >>>>also
    >>>>
    >>>>
    >>>>
    >>>>>>>>>>posed some other pertinent questions to Peter and I too would
    >>>>>>>>>>
    > be
    >
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>interested
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>>to see the answers...
    >>>>>>>>>>
    >>>>>>>>>>I also wonder just how much of a problem it would cause having
    >>>>>>>>>>
    > your
    >
    >>>>>>>>>>near-prime-vertical azimuths off by around 15 degrees? For a
    >>>>>>>>>>
    >>>>>>>>>>
    >>cluster
    >>
    >>
    >>>>of
    >>>>
    >>>>
    >>>>
    >>>>>>>>>>star sights, say, a prudent navigator would also be taking
    >>>>>>>>>>
    > sights
    >
    >>>>>>>>>>
    >>>>from
    >>>>
    >>>>
    >>>>
    >>>>>>>>>>objects far away from the prime vertical (to get useful angular
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>separation)
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>>and this would tend to mitigate any problems due to bad
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>near-prime-vertical
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>>azimuths. The inaccuracy of the tables near the prime vertical
    >>>>>>>>>>
    > are
    >
    >>>>>>>>>>
    >>>>also
    >>>>
    >>>>
    >>>>
    >>>>>>>>>>mitigated by being able to assess independently (in many cases)
    >>>>>>>>>>
    > in
    >
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>which
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>>>azimuth quadrant the celestial object sits.
    >>>>>>>>>>
    >>>>>>>>>>If your estimated position is pretty close (say, within 10
    >>>>>>>>>>
    > nautical
    >
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>miles)
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>>to your actual position then I cannot think of any
    >>>>>>>>>>
    > circumstances
    >
    >>>>>>>>>>
    >>>>where
    >>>>
    >>>>
    >>>>
    >>>>>>it
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>>>would significantly affect the sort of accuracy we would expect
    >>>>>>>>>>
    >>>>>>>>>>
    >>from
    >>
    >>
    >>>>CN
    >>>>
    >>>>
    >>>>
    >>>>>>>>in
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>>a small boat at sea, which is the sort of user the book was
    >>>>>>>>>>
    > aimed
    >
    >>at
    >>
    >>
    >>>>in
    >>>>
    >>>>
    >>>>
    >>>>>>>>the
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>>first place. I have not thought deeply on this problem and I
    >>>>>>>>>>
    > would
    >
    >>>>>>>>>>appreciate the thoughts of other listers who will have greater
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>insight
    >>>>
    >>>>
    >>>>
    >>>>>>on
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>>>this problem than I.
    >>>>>>>>>>
    >>>>>>>>>>The "short" method of sight reduction used by Bennett is
    >>>>>>>>>>
    > popular
    >
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>because
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>>>the computed altitude can be arrived at quite quickly. But a
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>different
    >>>>
    >>>>
    >>>>
    >>>>>>>>>>procedure is required to calculate an azimuth and this rather
    >>>>>>>>>>
    > takes
    >
    >>>>>>>>>>
    >>>>the
    >>>>
    >>>>
    >>>>
    >>>>>>>>>>gilt off this method. Ageton's method, by contrast, requires
    >>>>>>>>>>
    > more
    >
    >>>>>>>>>>
    >>>>steps
    >>>>
    >>>>
    >>>>
    >>>>>>>>to
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>>get to the calculated altitude, but the azimuth then drops out
    >>>>>>>>>>
    > very
    >
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>quickly
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>>and is accurate. Azimuth quadrant ambiguities are also easily
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>resolved.
    >>>>
    >>>>
    >>>>
    >>>>>>>>>>Too, only one set of tables is required for the Ageton method.
    >>>>>>>>>>
    >>>>>>>>>>Geoffrey Kolbe
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>-------------------8<---------------------
    >>>>>>>>>>From: George Huxtable
    >>>>>>>>>>The problem with these azimuth tables ...
    >>>>>>>>>>is not in their ambiguity, but in their inaccuracy, and that
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>inaccuracy
    >>>>
    >>>>
    >>>>
    >>>>>>>>is
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>>exactly what I have complained about. And there is not one
    >>>>>>>>>>
    > word, no
    >
    >>t
    >>
    >>
    >>>>>>>>>>
    >>>>>>even
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>a
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>>hint, in the book that major errors in azimuth can occur, for
    >>>>>>>>>>
    >>>>>>>>>>
    >>certain
    >>
    >>
    >>>>>>>>>>observations in a VERY wide swathe around East or West.
    >>>>>>>>>>-------------------8<---------------------
    >>>>>>>>>>>From Peter Fogg
    >>>>>>>>>>
    >>>>>>>>>>Inserted in second edition is . "In extreme cases the table
    >>>>>>>>>>
    > should
    >
    >>be
    >>
    >>
    >>>>>>>>>>interpolated when observations have been made in the vicinity
    >>>>>>>>>>
    > of
    >
    >>the
    >>
    >>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>prime
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>>vertical and/or LHA, declination and latitude require
    >>>>>>>>>>
    > substantial
    >
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>rounding
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>>off before using the table. When in doubt use the Weir
    >>>>>>>>>>
    > diagrams.
    >
    >>>>>>>>>>In practice you could happily sail across an ocean and never
    >>>>>>>>>>
    > notice
    >
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>this
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>>>supposed problem, particularly by following the common sense
    >>>>>>>>>>
    >>>>>>>>>>
    >>approach
    >>
    >>
    >>>>>>>>>>outlined previously. With nav. it it often a case of one system
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>checking
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>>>another. In fact taking sights and working out a fix is a check
    >>>>>>>>>>
    > on
    >
    >>>>>>>>>>
    >>>>the
    >>>>
    >>>>
    >>>>
    >>>>>>>>>>basic tool of running a DR.
    >>>>>>>>>>
    >>>>>>>>>>If the whole book has been subjected to the same searching
    >>>>>>>>>>
    >>>>>>>>>>
    >>criticism
    >>
    >>
    >>>>>>>>>>
    >>>>>>and
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>>>>>this rather inconsequential nit-pick is the only flaw found,
    >>>>>>>>>>
    > then
    >
    >>it
    >>
    >>
    >>>>is
    >>>>
    >>>>
    >>>>
    >>>>>>>>>>really a back-handed compliment to the book as a whole. A
    >>>>>>>>>>
    > ferocious
    >
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>critic
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>>>seems to think the rest works just fine.
    >>>>>>>>>>
    >>>>>>>>>>Border Barrels Ltd., Newcastleton, Roxburghshire, TD9 0SN,
    >>>>>>>>>>
    >>>>>>>>>>
    >>Scotland.
    >>
    >>
    >>>>>>>>>>Tel. +44 (0)13873 76253 Fax. +44 (0)13873 76214.
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>>
    >>>>>>>>>--
    >>>>>>>>>Courtney Thomas
    >>>>>>>>>s/v Mutiny
    >>>>>>>>>lying Oriental, NC
    >>>>>>>>>
    >>>>>>>>>
    >>>>>>>>>
    >>>>>>>>>
    >>>>>>>>>
    >>>>>>>>>
    >>>>>>>>>
    >>>>>>>--
    >>>>>>>Courtney
    >>>>>>>s/v Mutiny
    >>>>>>>lying Oriental, NC
    >>>>>>>
    >>>>>>>
    >>>>>>>
    >>>>>>>
    >>>>>>>
    >>>>>>>
    >>>>>--
    >>>>>Courtney Thomas
    >>>>>s/v Mutiny
    >>>>>lying Oriental, NC
    >>>>>
    >>>>>
    >>>>>
    >>>>>
    >>>--
    >>>Courtney
    >>>s/v Mutiny
    >>>lying Oriental, NC
    >>>
    >>>
    >>>
    >
    >
    > --
    > Courtney
    > s/v Mutiny
    > lying Oriental, NC
    >
    >
    
    
    --
    Courtney
    s/v Mutiny
    lying Oriental, NC
    
    
    

       
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