Does anybody out there have a method of doing ex-meridians? Examples of the Coast Guard questions would be great, but anything would be helpful. I’ve been trying to find some stuff online, but keep coming up blank. Thanks.
[QUOTE=New3M;69579]Does anybody out there have a method of doing ex-meridians? Examples of the Coast Guard questions would be great, but anything would be helpful. I’ve been trying to find some stuff online, but keep coming up blank. Thanks.[/QUOTE]
See below Russ
http://en.wikipedia.org/wiki/Ex-meridian
That uses a Haversine formula which I don’t think I really want to tackle. Isn’t there some method of using tables?
Bowditch Tables, pretty straight forward. A little double interpolation as I recall but not difficult.
If you don’t have Bowditch vol 2 yet, get one: it’s what you’ll have in the exam room.
I’ve got one. Just don’t have any idea where to start!
Read Bowditch and figure it out. Everything you need is there.
Ex-meridians used to be used regularly before SatNav and GPS, and are useful if the sun is obscured at LAN, but is visible within a few minutes on either side of LAN (usually about 20 minutes). In the old Bowditch, you entered Table 29 with Declination and Latitude to obtain a factor used to enter Table 30 along with the time between predicted LAN and the ex-meridian observation. That yielded a correction to add to the ex-meridian sight worked by normal LAN formula. It might sound complicated, but it is fast and easy, and we often used it to save a cloudy LAN.
Thanks for the guidance. I’ve been doing a bunch of the CG questions, but none of them seem to be working out. I’m using the right tables (in the new version of Bowditch), right almanac, etc. Yet I can’t get any closer than 10’ in my calculations (it’s not my math). Any other advice? I would think that their questions would work out if not exact, pretty close.