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» Online Classroom   »   » Public Discussion of Cel Nav   » Hawaii By Sextant, Problem 12

   
Author Topic: Hawaii By Sextant, Problem 12
climber


 - posted July 23, 2016 02:03 PM      Profile for climber           Edit/Delete Post 
After a hiatus I am back trying to navigate my way to Hawaii. I have a question concerning the unknown body sight in problem 12.

At 13:00:15 the bearing of the unknown body is 350 degrees true per page 16 of the book.

I can find the GHA Aries at 126 degrees 09.4 min. using the NA tables. So far so good. To use the Starfinder I convert the GHA of Aries to the LHA using the equation:

LHA Aries = GHA Aries - DRLong since my DR Long is West

Therefore:

LHA(A) = 126 degrees 09. 4 min. - 136 degrees 28.0 min.

Adding 360 degrees to 126 degrees 09.4 min. and then subtracting the 136 degrees 28.0 min. I get the LHA(A) to be 349 degrees 41.4 min.

Using the 35 degree north template for the Starfinder and setting the LHA(A) to 349.75 I can find the star Kolchab at about 350 degrees true and a declination of about 24 degrees. This agrees with the sight of the unknown body. So far no problem and my answer agrees with that in the book on page 30.

Now for my questions.

1. Why is this star unusable? The sight is worked out on pate 49 of the book but it is not plotted on page 83.

2. When I go to the table for July 13 and look up the declination for Kolchab it is N74 degrees 14.0 min. Why is this declination so much different than the declination provided by the starfinder which agrees well with the sextant sight?

I must be missing something obvious here but I can't put my finger on it.

Thank you.

From: apalachicola
Capt Steve Miller


 - posted July 23, 2016 03:16 PM      Profile for Capt Steve Miller           Edit/Delete Post 
The LOP for the Kochab sight when plotted was 20 miles from the intersection of the Venus and Moon LOPs indicating that the sight was bad.

Regarding the Declination of Kochab at N74° 14' that is correct. When you look at the Star Finder and see Kochab what you are looking at is the Altitude (not the Declination) and Azimuth of Kochab. These values would agree closely with the sight data as you stated.

From: Starpath
climber


 - posted July 24, 2016 01:30 PM      Profile for climber           Edit/Delete Post 
I understand now. I' forgot the definitions of declination and altitude.

Thanks

From: apalachicola


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