Astronomy

How to Observe the Changing Position of the Sun to Determine the Cardinal Points



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The movement of the Sun has been observed since time immemorial.  It rises in one direction, is at its highest in the middle of the day, and sets in the opposite direct, and does this every day without fail.  This constancy has allowed it to be used to set navigational directions, or cardinal points.

It must be stated at this point; that any observations made of the Sun must be done with caution.  Staring directly at the Sun can damage your eyes, and using any sort of magnification such as binoculars or a telescope, will cause permanent damage.  Always err on the side of caution, and if in doubt, don’t do it. 

The first thing you will notice when observing the Sun, is that it does not rise precisely in the east every day.  There are only two days a year when this happens, these times are called the equinox.   This is due to the tilt of the Earth’s axis.   Another factor that can affect the Sun’s position to determine the cardinal points are where you are regarding your latitude. 

The closer you are to the equator, the more the Sun will appear to swing around you.  So if you are in the southern hemisphere, the Sun will move from left to right, and point south at midday.  While in the north, it will swing right to the left.  So careful observation is necessary to determine your latitude.

For basic observing of the cardinal points using the Sun, you require a watch set at local time.  You will have to use a watch with hands, not a digital one.  In the northern hemisphere, point the hour hand at the Sun, and the point exactly halfway between the hour hand and 12 o’clock on the watch is south.

If you are in the southern hemisphere, point the 12 towards the Sun and the halfway point between the hour hand and 12 o’clock is north.  This will not give you exact cardinal point, but will certainly orientate sufficiently if you do not have a compass.

The Sun rises and sets at different times so to build up a more exact picture of the cardinal points, you will have to start with more equipment and a lot more research.  Get your hands on an almanac, diary, or newspapers, to give you a guide to the times of sunrise and sunset.  You will also need a chart to record your observations, and a drawing or printout of your local eastern and western landscape.  This should show a landmark and plenty of sky, as you will be recording in diagram form, the Sun’s positions at sunrise, sunset and at noon.

Use the same position for all your observations, and mark north and south on the diagrams.  You can then chart the precise time and position that the Sun rises and sets throughout the year.  At the end of your observations, you can then see how much variation there is in these times and the cardinal points. 

The Sun’s position may only vary by a few degrees, but understanding these variations will make your observations of the Sun’s changing position and how to determine the cardinal point more accurate.

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