SextantNavigation
In the event of an emergency when you lose your navigational electronics it would be useful to know how to navigate using a sextant. The simplest calculation is when you take a sun shot at local apparent noon (LAN).[1] [2]
Tools
- Sextant
- Mechanical clock set to Greenwich Mean Time (GMT)
- Some means of determining noon
- Celestial Sight Reduction Tables for Marine Navigation tables
Sun Shot at Local Apparent Noon
Latitude
To determine latitude:
- Point the sextant at the horizon
- Look through the tekescope
- Adjust the index mirror with the index bar until the Sun aligns with the horizon
- Read the angle from the arc
- Note the exact time
- Consult a celestial table to calculate the latitude
Longitude
To determine longitude using a chronometer at local noon:[3]
- Note the precise time of noon GMT
- Know the local noon time
- If local noon is before GMT noon you are on eastern logitutde
- If local noon is after GMT noon you are on western logitutde
Each difference of 4 minutes = 1 degree longitude
Other Sightings
Other sightings of the sun (not at noon), moon or stars are complex and beyond the scope of this article.