Carlos
I imagine some people still use Ageton's (H.O. 211) because it is readily available, often as a free download. In addition there are a number of variations of it available, also often for free. Aside from being available for free the other two "selling points" for Ageton's are that you do not have to learn how to derive an assumed position because you work from your DR position, and you don't have to interpolate.
I personally find all the additions, subtractions, and rules that must be applied as you work the sight using Ageton's are the source of many blunders even under ideal conditions (e.g. sitting at my desk after a good night's sleep and not having to worry about "sailing" my house.) I usually find it takes me several tries to get a correct sight reduction. This more than offsets the inconvenience of having to derive an assumed position -- which, once you "get it," is not hard to do. Others may not share my arithmetic "challenges" and may disagree with that assessment. To each his own...
Ageton's was (probably still is) available in Bowditch (American Practical Navigator) in what used to be Table 35. (Vol 2, circa 1981) The numbers of the Bowditch tables changed at one point when they went from the two volume format to all one volume -- they have since changed back to a two volume format but I have not researched if the numbers changed again or if they changed back to the old numbers.
In the original Ageton's it is said that a solution may be in error by 1 to 2 nmi when the meridian angle approaches 90° (this is the same as a LHA of 90° or 270°) The original also recommends that you toss out sights where the K value (an intermediate value you derive during the process) approaches 90°. This is often called "The Forbidden Zone."
In an article written in "The Astronomical Society of the Pacific (vol 56 No.3222 p. 149) titled "The Accuracy of Ageton's Method in Celestial Navigation" the author, S. Herrick, points out that errors of up to 6 nmi can be expected in "normal" ranges and up to 30 nmi may occur when you enter the "Forbidden Zone."
If you look in the "old" Bowditch Vol II in the front of the book they have an "Explanation of the Tables" section that addresses each table separately. Bowditch seems to agree with Herrick and states in the explanations section that although these are tables are generally used without interpolation that when the meridian angle, R, or K get to within 2° 30' of 90° then "interpolation of the B value of angle R..." (intermediate numbers used in the Ageton's process) "...alone reduces the errors to about 2 nmi. Therefore when K falls within 10° of 90° it is best to discard those sights or to interpolate the B value of R." I am paraphrasing here, the exact quote may differ slightly. Another commonly stated "positive attribute" of Ageton's was that you normally don't need to interpolate, but now that is negated.
By my own inspection of the tables the need to interpolate the B value of R occurs about when the A value used to look up R is less than 666 making it easy to recall a trigger of when you really should interpolate.
If you are a little lost on the alphabet soup here -- well that is the way Ageton's goes... Lots of A's and B's and K's and R's etc. most of which have "rules" associated with them, and since they are just intermediate values on the way to a final solution it is impossible to have any intuitive sense as to whether you are on the right track or not until you complete the process -- and if you are me, come up with a nonsensical answer 3 times out of 4. It's not Ageton's fault -- the method does work. The fault is entirely mine, but it still happens.
Frankly I find using the Ageton's tables to be tedious, and for me, prone to many blunders. Now that you can get Pub. 249 (or Pub. 229) as a free download right from from this site I see no reason to recommend Ageton's for sight reduction, and certainly not for new students.
And I also agree that direct calculation with an electronic calculator is a better approach these days, but it isn't a bad idea to learn how to use some sort of printed tables, especially if you expect to sit for an exam at some point.
But as before -- to each his own.
I imagine some people still use Ageton's (H.O. 211) because it is readily available, often as a free download. In addition there are a number of variations of it available, also often for free. Aside from being available for free the other two "selling points" for Ageton's are that you do not have to learn how to derive an assumed position because you work from your DR position, and you don't have to interpolate.
I personally find all the additions, subtractions, and rules that must be applied as you work the sight using Ageton's are the source of many blunders even under ideal conditions (e.g. sitting at my desk after a good night's sleep and not having to worry about "sailing" my house.) I usually find it takes me several tries to get a correct sight reduction. This more than offsets the inconvenience of having to derive an assumed position -- which, once you "get it," is not hard to do. Others may not share my arithmetic "challenges" and may disagree with that assessment. To each his own...
Ageton's was (probably still is) available in Bowditch (American Practical Navigator) in what used to be Table 35. (Vol 2, circa 1981) The numbers of the Bowditch tables changed at one point when they went from the two volume format to all one volume -- they have since changed back to a two volume format but I have not researched if the numbers changed again or if they changed back to the old numbers.
In the original Ageton's it is said that a solution may be in error by 1 to 2 nmi when the meridian angle approaches 90° (this is the same as a LHA of 90° or 270°) The original also recommends that you toss out sights where the K value (an intermediate value you derive during the process) approaches 90°. This is often called "The Forbidden Zone."
In an article written in "The Astronomical Society of the Pacific (vol 56 No.3222 p. 149) titled "The Accuracy of Ageton's Method in Celestial Navigation" the author, S. Herrick, points out that errors of up to 6 nmi can be expected in "normal" ranges and up to 30 nmi may occur when you enter the "Forbidden Zone."
If you look in the "old" Bowditch Vol II in the front of the book they have an "Explanation of the Tables" section that addresses each table separately. Bowditch seems to agree with Herrick and states in the explanations section that although these are tables are generally used without interpolation that when the meridian angle, R, or K get to within 2° 30' of 90° then "interpolation of the B value of angle R..." (intermediate numbers used in the Ageton's process) "...alone reduces the errors to about 2 nmi. Therefore when K falls within 10° of 90° it is best to discard those sights or to interpolate the B value of R." I am paraphrasing here, the exact quote may differ slightly. Another commonly stated "positive attribute" of Ageton's was that you normally don't need to interpolate, but now that is negated.
By my own inspection of the tables the need to interpolate the B value of R occurs about when the A value used to look up R is less than 666 making it easy to recall a trigger of when you really should interpolate.
If you are a little lost on the alphabet soup here -- well that is the way Ageton's goes... Lots of A's and B's and K's and R's etc. most of which have "rules" associated with them, and since they are just intermediate values on the way to a final solution it is impossible to have any intuitive sense as to whether you are on the right track or not until you complete the process -- and if you are me, come up with a nonsensical answer 3 times out of 4. It's not Ageton's fault -- the method does work. The fault is entirely mine, but it still happens.
Frankly I find using the Ageton's tables to be tedious, and for me, prone to many blunders. Now that you can get Pub. 249 (or Pub. 229) as a free download right from from this site I see no reason to recommend Ageton's for sight reduction, and certainly not for new students.
And I also agree that direct calculation with an electronic calculator is a better approach these days, but it isn't a bad idea to learn how to use some sort of printed tables, especially if you expect to sit for an exam at some point.
But as before -- to each his own.