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Re: Noon sun fix example
From: Hewitt Schlereth
Date: 2009 Sep 19, 10:05 -0400

Hi Jeremy -

Here's a paper-and-paper method of finding Longitude at Noon based on
the motion correction table published in Latitude and Longitude by the
Noon Sight.

My work sheet is the .doc attachment.
The table scan is the .jpg attachment.

As you'll see, this method differs from your 1300 GPS by .4' in Lat
and 4.3' in Lon.

Thanks for providing data from actual combat conditions. :-)

Hewitt

On 9/17/09, Anabasis75@aol.com  wrote:
>
> I shot a "Wilson-esque" sun around noon with the worse possible combination
> that I could get here on this voyage. Basically we were heading CRS 305 spd
> 7.6 knots (sailboat speed) in the middle latitudes (32 deg North) with the
> sun descending towards the celestial equator at 1.1' per hour and a
> declination around 3 degrees North.
>
> Instead of a 30 line spread over 30 minutes as I have done in the past, I
> tried a far more likely, and simple approach: 5 LOP's 2 before LAN, one "at"
> LAN, and two after.  They are shot as nearly equal intervals around LAN
> (within a few seconds).  They are nearly equal altitudes to boot, which was
> unintentional as I was taking them by time not by arc.
>
> I plotted the lines by standard trig reduction on the computer and gave a
> very reasonable fix error at 1300 of 0.3 nm.
>
> Here's the data.
>
> Height of eye 103 feet
> Index correction -1.2'  (IE 1.2' on the arc)
> Standard Temp & pressure
> Sun, all lower limb observations.
> Crs 305 deg True
> Spd 7.6 knots
> ZD +4
> 15 September 2009
>
> GPS fix at 1300 Lat 32 deg 4.7' North; Long 075 deg 33.1' W
>
> Data
> Time (LT)         Hs
> 12h 47m 45s    60 deg 33.8'
> 12h 52m 17s    60 deg 37.6'
> 12h 56m 48s    60 deg 38.4'
> 13h 00m 17s    60 deg 37.4'
> 13h 05m 48s    60 deg 33.4'
>
> Find the 1300 fix by observation.  (please attach any graphs if that is the
> method of solving)
>
> Jeremy
>  >
>

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File: 109803.jeremy-noon-lat-lon-hs.doc

File:

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