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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@LISTSERV.WEBKAHUNA.COM] On Behalf Of Courtney
> Thomas
> Sent: Saturday, September 13, 2003 7:46 AM
> To: NAVIGATION-L@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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