# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

**Paper Calc. Noon**

**From:**Doug Royer

**Date:**2004 Aug 4, 10:16 -0700

Here is something to think about. The accuracy will be suspect.It will give you an idea of your noon time or at least an idea to think of the problem an other way. 2 things must be known to do this: S.R. and S.S. Lat and the Sun's dec at these times.There are ways to calculate the expected sun's dec but I'm not going there now. The accuracy of this will largely depend on how well you keep your dr(compensating for leeway,set/drift etc). After your noon pos is plotted and you have an idea of its time get up on deck and 30 min before and after calculated time follow the procedure to take the noon sight. When at sea you can estimate the time of sun rise or sunset after a few days of observation. Here it is: Plot the dr pos at the estimated time of S.R.Take the Lat. Extend the trackline for the daily run to the time of calc. S.S. and plot the dr. Take that Lat. Find LMT of S.R. and S.S. LMT = ((180 + - t)/15) +t = sunrise -t = sunset +d sn -d cn t = cos-1((sin - 0.84 - (sin L x sin d)/(cos L x cos d)) Now you know the LMT of sr and ss Find the lenght of daylight ex; ss at 1850,sr at 0635. add them to find daylight = 12 h 15 min divide that by 2 to estimate LMT of noon. calculate and plot the LMT noon pos. Find the center long of the ZD closest to the dr long. Convert LMT to ZT: subtract the smaller long from the larger long to find delta long.(remember where your dr long is in relation to the center long of ZD) Convert delta long to delta time: delta long/15 = delta time ZT of Noon = LMT + - delta time c. long ZD W of dr long: - delta time c. long ZD E of dr long: + delta time Plot the ZT noon pos on the trackline and find the Lat and Long. You now have an idea of the ZT of LAN and and the dr long.You can use the noon sight procedure or use the dr long to calculate GMT. Try it out.Refine it if you wish.