The lower-limb sun sight should be relatively benign, but we will review the process nevertheless, so we can reinforce our understanding.
Hs 19 degrees 53.5 minutes
Dip (-) 4.3 minutes
App alt 19 degrees 49.2 minutes
3rd corr (+) 13.6 minutes
Ho 20 degrees 2.8 minutes
GHA 71 degrees 56.2 minutes
Inc and corr (+) 7 degrees 2.5 minutes
GHA 78 degrees 58.7 minutes
(-) Assumed longitude 29 degrees 58.7 minutes
LHA 49 degrees
I chose an assumed longitude of 29 degrees 58.7 minutes because it is closest to the DR longitude of 30 degrees W.
Declination is S 19 degrees 0.2 minutes, and the d correction is (-) 0.6 minutes
Dec. S 19 degrees 0.2 minutes
Dec. S 18 degrees 59.9 minutes
Enter H.O. 249 Vol. 2, page 203:
There is no d correction, as I rounded off the declination to 19 degrees.
Intercept is 0.2 minutes Away, as Hc is greater than the Ho.
Inc 5 degrees 52 minutes
+V (from Increments and corrections page xiv of the Nautical Almanac) +5.7
LHA 358 degrees
I add 360 degrees to the GHA when I subtract the assumed longitude to get a positive number. (You can see that the assumed longitude is greater than the GHA; therefore, we add another whole circle, 360 degrees, to the GHA so that we can get our LHA.)
We have now an assumed position of 33 degrees N by 30 degrees 45.2 minutes W.
The declination of the moon is listed as S 5 degrees 50.1 minutes. The d correction is subtracted, as the declination is decreasing as we can see by inspection. The d correction is -6 minutes, so the final declination is S 5 degrees 44.1 minutes.
The HP is the Horizontal Parallax and is used for the 3rd correction for the moon, which includes parallax, semidiameter and refraction.
To reduce the Hs to Ho, we do the following:
-dip 4.3 minutes
3rd corr + 46.3 minutes
+ 3.4 minutes for upper limb
51 degrees 43.2 minutes
30 minutes (for upper limb sight always subtract 30 minutes as per directions)
Now we can enter H.O. 249 Vol. 2, page 200. My assumed latitude is 33 degrees N and assumed longitude is 30 degrees 45.2 minutes
Hc 51 degrees 57 minutes d -60 Z 177 degrees
Go to Table 5 for 44 minutes of declination, which equals 44 minutes. This is subtracted from the HC as noted by inspection. The final Hc is 51 degrees 13 minutes.
Whew! Look over what I have done and see if you can follow it. If you are unfamiliar with moon sights, go to Mixterï¿½s or Bowditch and review the process. The final step in this process is to plot the position using the assumed positions of the sun and moon. The fix is right on the DR. Capt. McMillan was a good shot.
As always, contact me with any questions.
D: 0.02′ Toward
E: 33 degrees 01′ N by 29 56′ W