A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brad Morris
Date: 2015 Oct 10, 00:36 -0400
The lower right hand of the page is Auxiliary and Planning data.
The time given for the meridian passage is for the CENTRAL meridian of your time zone. You will have to adjust the actual time of meridian passage by the difference in longitude between YOUR meridian and the CENTRAL meridian. Take the difference (in degrees) and multiply by four minutes. Add or subtract the result to the time in the almanac, depending upon east (subtract) or west (add) of the central meridian.
Don't forget that the time given is for standard time, not daylight savings time.
Now you will also note that the time is always rounded off to the nearest minute. That is primarily because the change in altitude around meridian crossing changes very slowly, so great precision is not needed in the publication. In practice, you will begin observing before meridian crossing, taking observations until after the expected meridian crossing. The greatest altitude measured will be very close to the meridian crossing.
Want more accurate planning data? (maybe using it for something else?). Then go the the U S Naval observatory site and the planning data, given your latitude and longitude will yield the meridian crossing to the second. Depending upon the sun's declination and your N/S latitude, the azimuth to the body will always be either 0° (due north of you) or 180° (due south of you) for meridian crossing.
There is also a lower meridian crossing. Consider, the sun crosses your complete circle of longitude around midnight on what is called the lower meridian. For high latitudes, you can sometimes observe the sun and moon on the lower meridian. Even high declination stars can be observed on the lower meridian!!
Welcome aboard. I hope you have your question answered. If not, write back!