07-03-2018, 03:46 AM
07-03-2018, 12:09 PM
Joe,
Table 5 is used to correct the declination change that is found in using Pub. No. 249. The "d" value found in the middle column of each page of latitude, in Pub. No. 249, is used, along with the minutes of declination (not degrees) that you obtain from The Nautical Almanac for the date and whole hour time of the sight you took. When using Table 5, it doesn't matter which row (at the top) or column (right or left side) you put the "d" value in or the minutes of declination- you'll get the same result.
Another way to think about it is this- you must correct the GHA for minutes and seconds since we rarely, if ever, take a sight right on the hour. So too with declination. Declination changes all the time so you have to correct for that change over time. The "d" value found in 249 and the minutes of declination are the figures used to find the declination correction in Table 5 which is either added or subtracted from Hc (found in 249) to get the final Hc value.
You can read more about it, and how to get it, here;
https://www.thenauticalalmanac.com/Compl...pdf#page=8
And here-
https://www.thenauticalalmanac.com/Compl...pdf#page=7
We're out sailing so I might not be able to reply promptly.
Cooler days,
Johannes
Table 5 is used to correct the declination change that is found in using Pub. No. 249. The "d" value found in the middle column of each page of latitude, in Pub. No. 249, is used, along with the minutes of declination (not degrees) that you obtain from The Nautical Almanac for the date and whole hour time of the sight you took. When using Table 5, it doesn't matter which row (at the top) or column (right or left side) you put the "d" value in or the minutes of declination- you'll get the same result.
Another way to think about it is this- you must correct the GHA for minutes and seconds since we rarely, if ever, take a sight right on the hour. So too with declination. Declination changes all the time so you have to correct for that change over time. The "d" value found in 249 and the minutes of declination are the figures used to find the declination correction in Table 5 which is either added or subtracted from Hc (found in 249) to get the final Hc value.
You can read more about it, and how to get it, here;
https://www.thenauticalalmanac.com/Compl...pdf#page=8
And here-
https://www.thenauticalalmanac.com/Compl...pdf#page=7
We're out sailing so I might not be able to reply promptly.
Cooler days,
Johannes
07-03-2018, 01:11 PM
(07-03-2018, 12:09 PM)CelNav57 Wrote: [ -> ]Joe,
We're out sailing so I might not be able to reply promptly.
Cooler days,
Johannes
Thanks for the reply - table 5 makes sense now; its the paper version of dec increments/60 X +-d. (the first correction to declination.... right?)
As long as you are out sailing send me an observation of the sun or moon with DR pos and Ill post it in the CN Challenge thread...:)
Happy sailing
joe