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» Online Classroom   »   » Public Discussion of Cel Nav   » Found the error and more (I think)

   
Author Topic: Found the error and more (I think)
jehan


 - posted November 13, 2007 05:29 PM      Profile for jehan           Edit/Delete Post 
The sight reduction example no 2 page 11-39
contains an embarassing typo. The NAO tables read 53 59 and not 53 49 as printed. Looks to me this problem was fudged or worked backwards since all the other numbers agree and so does the calculator reduction.

On the next page NAO example number 3 the latitude is given as 45 south and the declination 6 north. I understood that these are termed contrary signs and therefore the declination should be substracted....Unless I am wrong the reduction printed is for a same hemisphere situation....

Would very much like an expert opinion on the above as I am totally inexperienced in these matters and somewhat baffled........
jb

From: north bay on
David Burch


 - posted November 13, 2007 06:05 PM      Profile for David Burch           Edit/Delete Post 
Thank you we will check this immediately.

However i have to point out that the term "fudged" can sometimes imply some level of deception or making up numbers to get some desired result. I can assure you that there is absolutely nothing of that kind in any of our course materials.

There could well be an error—there are a lot of numbers in these materials—and there are in some places special examples created from numerical solutions as opposed to actual sextant sights, but none of these is ever fudged in any of the common senses of the word. That would be counter-productive in educational materials.

My guess is you did not mean the word that way, but this is a public forum and we must defend our long established standards against any misinterpretation.

This, by the way, is especially important with this set of sight reduction tables. They are a valuable short cut to more precise solutions, so we in fact try to check how they agree with the more precise solutions at every opportunity.

Back shortly when we sort this out.

From: Starpath, Seattle, WA
David Burch


 - posted November 13, 2007 08:10 PM      Profile for David Burch           Edit/Delete Post 
You are right. There is a typo in example 2. The H' should be 59', not 49'. The rest of the problem is correct as is. This was a transcription error. we work the problems on paper and copy to the electronic form for ebook and printing. I am surprised, however, that this has set there for so long without having been spotted. Thanks for finding and reporting this. We have added it to the errata in the Tech support section.

You are doing the right thing, by working these examples carefully. These NAO sight reduction tables are very good and should be a serious consideration as a primary method.

Example 3 seems to be right as is. If there are further questions on it, please clarify and we will go over it more.

From: Starpath, Seattle, WA
David Burch


 - posted November 13, 2007 08:25 PM      Profile for David Burch           Edit/Delete Post 
Just noted something... I think you mean #4, not #3, as that is the one with dec 6°... and there does look like something wrong in that one as well.

back shortly.

From: Starpath, Seattle, WA
David Burch


 - posted November 13, 2007 08:35 PM      Profile for David Burch           Edit/Delete Post 
thanks again. The declination in #4 should be South. the wrong letter is circled. Same likely source of error. rest of the problem is correct as shown.

Now i wonder if anyone is working these NAO problems! These have been in this new format for several years now. we will add some incentive somewhere along the line to encourage others to try these.

The fact is, once the paper work is under control, the optimum way to do cel nav is with a calculator or PC program such as the StarPilot, and then use these NAO tables as the back up method since you only need to carry that one book along as a full back up system.

From: Starpath, Seattle, WA
jehan


 - posted November 14, 2007 04:29 AM      Profile for jehan           Edit/Delete Post 
mille pardon,(my apologies), lo siento, English is my third language and far from being mastered. The connotation in french is indeed different. Section 11 is a most worthwile addition to your course. Like my response, however it did need revision.
jehan

From: north bay on
David Burch


 - posted November 14, 2007 11:24 AM      Profile for David Burch           Edit/Delete Post 
Thank you for that note. I was confident the word was not meant in a negative manner.

A great beauty of the online course is it reaches across the globe and we get to share the experiences of mariners from around the world.

Thank you again for finding these two errors in the notes. They are now in our tech support section on the course, and will be fixed in the next edition of the materials.

From: Starpath, Seattle, WA


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