12-20-2015, 12:32 AM
(12-19-2015, 01:34 AM)craigsl Wrote: If your chronometer is broken and time is unknown or you can't get a WWV or WWVH signal you're going to have a hard time determining Longitude. Latitude can be obtained easily enough from the blessed noon-sight. No time...no position fix.
Have any of you tried "the recovery of time" technique. I think it requires a known position and the GHA deriving the Hc specific to the position. Beyond that, I know nothing about.
Looking at Bowditch Chapter 26 Emergency Navigation
"Section 2612. Finding Longitude" (page 10) mentions something about determining meridian transit time and correcting the chronometer for same. There has to be some explanation for this?
I hope.
Craig
Bowditch Chapter 26 page 10 says,
"Either of these methods can be used in reverse to set a
watch that has run down or to check the accuracy of a watch if the longitude is known."
That's the difficult part if you don't know your longitude- you can't use GHA to calculate time.
But if you do know you Longitude here's the formula to assist you in determining time-
Determine GHA (with knowns of Hc or Ho, Ap. Lat., Declination & Ap Long)
(360 - Cos-1((Sin(Hc) – Sin(AP Latitude) x Sin(Declination)) / Cos(AP Latitude) x Cos(Declination)) + Longitude) - 360
The 360º figure is only if Body azimuth is less than 180 (before MP).
Wish I could be of more help.
Larry