NavList:

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.

From: Alan <alan202@verizon.net>
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

----------------------------------------------------------------
NavList message boards and member settings: www.fer3.com/NavList
Members may optionally receive posts by email.
To cancel email delivery, send a message to NoMail[at]fer3.com
----------------------------------------------------------------