NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: the answer...?
From: Jim Manzari
Date: 1998 Sep 28, 14:12 EDT
From: Jim Manzari
Date: 1998 Sep 28, 14:12 EDT
Russell Sher wrote: > > Hi - I think that the nav. list seems to be on the blink (or just quiet??) > > So - what was the answer the the noon sight question ( two suggestions below > from Joe and myself...) Russell and Joe, I was wanting to see if more answers might come in. Nothing...so it looks like the winner is Joe Shields. The ship is moving on a nearly south to north line. The relative motion -- ship + sun -- causes the sun to reach its highest altitude _before_ local apparent noon. The clue to the question is the 16kts ship speed. Had it been a slower vessel, say a yacht sailing at 5kts, this effect would be very difficult, indeed, to detect. Here's a bit of the conversation between the ship masters and a further twist on the subject of noon sights...comments welcome. -------- ...I consider myself to be a reasonably experienced (celestial) navigator, but I am puzzled by the problem. The only explanation that I can think of, is that you were on a heading directly opposite to the sun (I confess that I am not familiar with the geography of the area between Mauretania and the Schedlt) and thus the sun appeared to be decreasing in height but still approaching your meridian. And now, I have to add a bit of my own opinion regarding the noon sun shot. Before I commence, put on your armour, get your daggers ready for I am about to utter a bit of heresy. The noon sun shot is overrated. It's beauty lies in the simplicity of the calculations required to obtain one's latitude, but that is where it ends. One can easily take a few quick observations at "around" noon hour, reduce the sight as normal and plot the resultant east-west LOP on your chart to obtain your latitude. This method is particularly useful at high latitudes where the trajectory of the sun's passage tends to be fairly flat and determining the exact moment at which the sun reaches its maximum height can be somewhat subjective. In the winter time here in Iqaluit, I have sat outside, freezing my tail off, for up to 45 minutes, waiting for the sun to reach its maximum height of 3 degrees above the horizon. Even in the mid-latitudes, I have seen people up on deck taking observation after observation, trying to determine the exact moment of meridian passage, and even after all of that, there is no guarantee of a satisfactory result; I have rarely seen two people obtain the same numbers. I am not suggesting that the noon sun shot should be discarded - I still like to perform the operation - but it is not the be all and end all. Ok, allow me to put on my bullet-proof suit....fire away folks! =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-= =-= TO UNSUBSCRIBE, send this message to majordomo@XXX.XXX: =-= =-= navigation =-= =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-=