NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Pointers
From: Bill B
Date: 2004 Oct 9, 14:47 -0500
From: Bill B
Date: 2004 Oct 9, 14:47 -0500
> Can anyone explain me that the "Pointers" are? > I mean this is something in the sky, > probably a group of fixed stars. > > I just read a funny paper: > Joel Brenner, Determination of latitude in an emergency, > American Math. Monthly, 51, N 6 (1944) 343-244. > > The author recommends a method of determination of latitude > without almanach, without any tables, using only a sextant > and Polaris (and the "Pointers"). True that the Big Dipper can "point" you to Polaris. There is one other technique needed for lifeboat navigation with a sextant and no almanac. As you know, Polaris it not exactly at the pole. If memory serves me its declination is approx. 89d 16' now. So approx. 44' from the pole. Trick here is to know in which direction at a given time. Currently Kochab's 137 SHA is pretty close to 180d away from Polaris's SHA and visible all night at your latitude, so the pole lies between them. That relationship can help you determine whether Polaris is above, below, or lateral to the pole to adjust your Ho to latitude. Positions between must be interpolated, a simple matter for someone with your skill sets. If you move a bit past (approx. 13d) the end of the Big Dippers last "handle" star, this conceptual point can also serve as a rough "pointer" for a line segment through the pole and Polaris. You may also wish to visit the list archives around Sept 2004 under "Beginner Meridian Passage Question." Bill
