# NavList:

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

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Re: Sunset 3-body fix exercise
From: Peter Hakel
Date: 2011 Jan 16, 19:11 -0800
From this set of Jeremy's data (taking the date January 9) I calculated the following (see the attached image:)

1) The "many-body fix" at UT=13:30:00, marked with "X" on the plot (with vessel motion accounted for):
Lat:  S 6d 58.9'
Lon: E 72d 20.8'

2) The three pairs of LOP crossings ("two-body fixes"), (without vessel motion for simplicity, the time interval is less than 3 minutes):

Sun-Jupiter:
Lat:  S 7d 00.0'
Lon: E 72d 21.6'

Sun-Moon:
Lat:  S 6d 56.8'
Lon: E 72d 20.3'

Jupiter-Moon:
Lat:  S 7d 45.8'
Lon: E 72d 12.6'

and placed them on the chart.

3) I ran the three LOPs through these points, which results in a rather tall and thin cocked hat.  The computed many-body fix is located inside the triangle near the two Sun vertices.

4) Using the AP:
Lat:  S 7d
Lon: E 72d

I computed the following intercepts and azimuths

Sun:       19.8A   247.7d
Jupiter:   21.1A   280.3d
Moon:    19.4A   278.4d

and convinced myself of their consistency with the LOPs already plotted on the chart.

5) I placed Jeremy's DR on the chart; the longitude is about the same as the two Sun fixes but it does lie just outside the cocked hat near the Jupiter LOP.

Peter Hakel

From: "Anabasis75@aol.com" <Anabasis75@aol.com>
To: NavList@fer3.com
Sent: Sun, January 16, 2011 4:06:30 AM
Subject: [NavList] Sunset 3-body fix exercise

Since people have sharpened pencils at the ready, here is the second Bonus Exotica evolution.

It's a 3-body daylight fix shot around the time of sunset.  The time was recorded as the LL of the sun touched the visible horizon as seen through my 7x scope and shades.  Just prior to the sun observation, a LOP of Jupiter was taken, and just as the sun was crossing the horizon, a LL of the Moon was taken.

Sadly this isn't a great fix.  The sun is way off, and the moon had a thunderstorm right below it so the horizon was terrible.  Still, it was a fun exercise

Here's the Data:

Lat 7 deg 13.7' South
Long 72 deg 19.2' East
Temp 78 deg F
Pressure 1008 MB
Crs 038 deg true
Spd 12.2 knots
IC -0.8'
HoE 106 feet
ZD -6

Sun (LL)
Hs 0d 0.0'
Time (local) 19 hr 31m 08s

Jupiter
Hs 64 deg 49.8'
Time 19h 29m 14s

Moon (LL)
Hs 51d 07.8'
Time 19h 31m 52s

Jeremy

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