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The Southern Cross

Just as we can use the Pole Star in the northern hemisphere to find the direction of north, we can use the Southern Cross in the southern hemisphere to find the direction of south.   However, whereas we can use the … Continue reading

The Relationship Between Longitude, Latitude and the Nautical Mile.

The Relationship Between Longitude and the Nautical Mile.  The Earth’s equatorial circumference is 21640.6 n.m.  Since the Equator is a great circle, 1o will subtend an arc of:  21640.6 ÷ 360 =  60.113  ≈ 60 n.m. There are 360 meridians of Longitude so … Continue reading

Calculating the Sun’s Declination in a Survival Situation

In an ideal situation, we could find our latitude by using a satellite navigation system.  If sat-nav is not available, we can use astro navigation to calculate our latitude by the method shown at the following links: Latitude from the … Continue reading

Planning Star and Planet Observations

I have been asked about using ABC tables to calculate azimuth and altitude when planning star and planet observations.  Unlike the Sun and the Moon which are easily identified, the approximate positions of stars and planets need to be established … Continue reading

Astro Navigation In A Survival Situation

In a recent survey, the majority of people questioned were surprised to learn that astro navigation can be used in a survival situation.  In the same survey, 60% said that they would use satellite navigation systems to find their way … Continue reading

Finding Latititude In A Survival Situation.

The  full method of calculating your latitude from the altitude of the Sun can be found at this link.  However, in a survival situation, the following simplified method can be used. Equipment Needed.  A clinometer or other device for measuring angles. … Continue reading

Astro Navigation – What is it and why do we need it?

Astro-navigation (or celestial navigation as it is also known) is a fascinating subject that encompasses many areas of knowledge including geography, astronomy, history and mathematics.  As you unravel the principles and techniques upon which navigation is based, you will be … Continue reading

Finding Longitude In A Survival Situation.

We know that the Earth revolves about its axis once every 24 hours.  In other words, the Sun completes its apparent revolution of 360o in 24 hours.  This means that the Sun crosses each of the 360 meridians of longitude once … Continue reading

Latitude from Polaris

Using The Pole Star (Polaris)  To Find Your Latitude Assume that the Pole Star (Polaris)is exactly in line with the Earth’s axis produced, as shown in the following diagram. To an observer O on the Equator (lat. 0o) the Pole … Continue reading

Spherical Trigonometry Introduction

In the diagram above, the inner circle represents the Earth and the outer circle represents the celestial sphere.  Point N represents the North Pole, B represents an observer’s position on the surface of the Earth, and U represents the geographical … Continue reading