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» Online Classroom   »   » Public Discussion of Cel Nav   » Pub 249 declination values

Author Topic: Pub 249 declination values

 - posted February 16, 2015 08:38 AM      Profile for brokesailor           Edit/Delete Post 
Why do declination values only go up to 29 degrees? There are stars whose declination value is higher than that.
From: ChesBay
Capt Steve Miller

 - posted February 16, 2015 08:43 AM      Profile for Capt Steve Miller           Edit/Delete Post 
The short answer is that Pub 249 covers Bodies that are within 29° of the Ecliptic. This would include the Sun, Moon, Planets and Stars with Declinations less than or equal to 29°.
If one uses Vol. 1 of Pub 249 you will find Stars included that have Declinations over 29°.

From: Starpath
David Burch

 - posted February 16, 2015 09:47 AM      Profile for David Burch           Edit/Delete Post 
The other options are the NAO tables and Pub 229 or sight reduction by computation as done at www.starpath.com/calc and numerous other options that can be downloaded at no charge... such as celestial tools
From: Starpath, Seattle, WA

 - posted December 08, 2017 03:16 PM      Profile for Lou           Edit/Delete Post 
This is regarding "d" value corrections, in Box 5, when reducing star sights.
When using H.O.249 Volume 1, there seems to be no "d" value correction for Box 5, noted between star Hc and Z, as when using Vol. 2 and 3.
Why do we correct with Vol. 2 and 3, but not Vol. 1?
I can find no H. O. 249 Vol. 1, examples in either the first or second edition of Cel' Nav'.
There is a Chap 11, reference in Chap 6, but no explanation.

From: San Diego
Capt Steve Miller

 - posted December 08, 2017 03:35 PM      Profile for Capt Steve Miller           Edit/Delete Post 
Pub 249 Vol 1 contains the Hc and Zn with all corrections included.These are Final Answers - the only values you put in Box 5 is the Hc and Zn.
Vol 2&3 do not have the corrections applied, thus you have to fill in everything in Box 5.

From: Starpath

 - posted December 10, 2017 03:45 AM      Profile for Lou           Edit/Delete Post 
Captain Miller, thanks.
Regarding "d" value corrections, I suspected that H.O. 249 Vol.1 "d" corrections were included, but it's been forty plus years, since I went through U.S.A.F Nav' School. I simply couldn't remember and in addition, I believe we worked exclusively with Volume 1.
The process then seemed actually simpler, as being all aircraft related, using timed bubble sextants, negated several of the processes and the twilight restrictions necessary to nautical navigation.
Again, thanks!

From: San Diego

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