Sometimes, when operating in a Hostile Environment, you might need to travel at night. The decision to travel at night could be motivated by security considerations or simply weather conditions, as cloud, rain and temperature could provide you with suitable cover for safe movement.
In such situations, you might not have a compass or be able to see the sun, in which case you need to navigate with the stars.
Celestial navigation, based on a clear and starry night, is relatively straightforward. However, as the stars and constellations are constantly moving, you need to determine a fixed location that helps you orientate to either the north or the south point.
The North Star is almost immobile and is always located in the polar sector of the sky and points due north.
However, in the Southern hemisphere, the Southern Cross is your point of reference. To determine the direction of the Southern Celestial Pole (i.e. south), use the star pointers seen to the left of the Cross. Imagine a line between these two star pointers and construct a perpendicular line which will intersect with the axis of the Southern Cross. The point at which these two lines meet will give you the direction to the South.
Once you have determined either North or South (depending on the hemisphere on which you are located) you can then identify the other cardinal points on your mental compass.
Despite the use of GPS and related navigation instrumentation, the ability to use celestial navigation is a necessary survival skill. During a 1950s lecture by the late Henry Neeley (a lecturer at New York’s Hayden Planetarium), he noted that:
“The navigational use of the stars will continue to be a valuable asset for many years to come. In spite of all the scientific aids that have been developed to do the navigating by robot science, the ancient stars will still be a ‘must’ for a navigator or pilot” (sic).
On our HEAT courses, we teach the techniques of navigation, not only by day but also by night. During the star navigation module, we teach you not only how to navigate with the stars but also how to study the moon. Often, by watching from where the moon comes and goes, and by noting the time of day that you can see it, you will develop a better understanding of your environment and your orientation by the stars.
When the moon is on the same side of the Earth as the sun, the shaded side faces towards the Earth. When the moon is on the opposite side of the Earth to the sun, then you can see the full surface of the moon which is caused by the sun’s reflection.
Based on this understanding, you will know that:
- If the moon rises in time with the sun, then it will show a full moon.
- If the moon rises after the sun, it will show illuminated on your east side.
- If the moon rises before the sun, it will show illuminated on your west side.
Also, there are 57 other stars used by navigators worldwide and selected because of their ease of identification and wide spacing.
Stars can yield your circle of position on the Earth’s globe when seen above the horizon during twilight. By measuring the altitude of one of these stars above the horizon during twilight, you will be able to plot your position on this circle, if you can see a star at a certain altitude at a given time.
To be visible against the twilight sky, the majority of these 57 navigation stars are second magnitude or brighter, bearing in mind that the lower the figure of magnitude, the brighter the star.
When you want to determine your orientation by the stars when walking at night, you can also use local weather patterns to help you on your journey. Consider buying a Nautical Almanac and Air Almanac to study the position and movements of celestial bodies and enable you to use celestial navigation to determine your position, based on the sun, moon and planets.