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» Online Classroom   » Celestial Navigation   » Public Discussion of Cel Nav   » CelNav 2nd ed. problem 9.5 via NAO tables

Author Topic: CelNav 2nd ed. problem 9.5 via NAO tables

 - posted April 01, 2020 03:57 PM      Profile for Lance           Edit/Delete Post 
Has anybody done problem 9.5 in Celestial Navigation 2nd ed (David Burch, Starpath) using the NAO tables and reproduced the answer given?

Using the pub 249 excerpts in the book I get the correct solution given on page 237. Using the NAO tables I'm out by 10.2 nm (a=35.5 vs the correct answer of a=25.3 nm). This seems too large an error to blame on the tables. The NAO tables worked fine for problem 9.6.

From: Hobart, Australia

 - posted April 01, 2020 10:58 PM      Profile for Lance           Edit/Delete Post 
OK, folks, abject apologies for my newbie error! I finally started again from a clear form and realized my mistake. It was in C2, the second correction. I entered the table from the top row - correct, but from the left hand column - incorrect. I should have read the Z2° from the right hand column. So C2, while remaining negative, should be -3, not -14.

I repent in sackcloth and ashes. :-(

From: Hobart, Australia
David Burch

 - posted April 02, 2020 08:48 AM      Profile for David Burch           Edit/Delete Post 
No Problem. Glad it worked out.

In passing, we have a (PC) tool online that lets you check all the intermediate steps to be sure our N(x) solution is executed properly. See link at:

This checker is the work of the late Stan Klein, who had done so very much to benefit navigators over many years.

For those who might see this note, let me point out that our N(x) tables is the world's shortest sight reduction tables. It was originally presented as part of our Emergency Navigation Card

From: Starpath, Seattle, WA

 - posted April 02, 2020 02:12 PM      Profile for Lance           Edit/Delete Post 
I also found the CelestialTools.exe program on your web site. This allows checking of sights calculated with the NASR tables, which I presume are another name for the NAO tables. I downloaded my set of NAO tables from your website - are these the pre-1999/post-2004 set?

A suggestion: I wonder if it would be worthwhile adding a little reminder to forms 106 and 108 to help people avoid the mistake I made (I made the same mistake more than once, must be getting dementia). I've attached a tentative revision for the relevant boxes.

From: Hobart, Australia

 - posted April 03, 2020 03:10 AM      Profile for Lance           Edit/Delete Post 
I also have an edited version of a universal plotting sheet, set up for my use in the southern hemisphere (I just edited the minute labels, as they are simply text objects in the pdf, easily changed). Obviously I can't attach it but I can send it to you if it's of any interest.

Regarding the NAO form, all I did was to add text lines below box 3 - "(Use LEFT column for P°)" and below box 4 - "(Use RIGHT column for Z2°). Hopefully the reminders will stop me from making that mistake again!

From: Hobart, Australia

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