Astronomy how to Observe the Changing Position of the Sun to Determine the Cardinal Points

Janette Waldron's image for:
"Astronomy how to Observe the Changing Position of the Sun to Determine the Cardinal Points"
Image by: 

Scientific evidence suggests that early man carefully observed the rising and setting of the sun. They were said to recognize that the sun does not rise and set just anywhere. Those who note the changing position of the sun can observe the patterns which help establish the cardinal directions. The four cardinal directions (or points) as known by scientists, are north, south, east and west. Cardinal points are deemed the foundation of a structure one can utilize to find specific places. The cardinal points are frequently used for geographic orientation and they can be calculated anywhere on a rotating astronomical body. North and south point to the poles which are defined by what is called ‘the axis of rotation’.

East and west point orthogonally along as well as opposite, the direction of rotation. The intermediate points which lie between the four cardinal directions form what is called the ‘compass rose’ as well as the points of a compass. NE, NW, SW and SE are deemed the intermediate directions. South is always directly opposite the north. An observer who is facing north while standing upright, will have east and west to the right and left respectively. Therefore the majority of devices for finding orientation usually operate by finding north first. The position of the sun sitting in the sky is often used for orientation by astronomers, scientists, sailors and a myriad of people. (More accurately when the general time of day time is well estimated).

The sun rises in the east in the morning then tracks upwards. The sun sets in the west in the evening. It is to the south in the middle of the day for those who live in the northern hemisphere and vice-versa for those who reside in the southern hemisphere. The closer to the equator one is, the better this specific method works. More so between the Tropic of cancer and the Tropic of Capricorn. But a more accurate estimation can be made when one factors in the approximate latitude and time of the year. Irrespective of your location, the earth’s axial tilt ensures that there are only two days annually when the suns rises precisely due north. These days are called equinoxes. (All other days are dependent on the time of year it is). The sun will rise either north or just south or true east. It then sets north or south of true west.

All locations have the sun rising north of east and setting north of south from March equinox through to the September equinox. From the September equinox it rises south of east and sets west of south until the March equinox. Those studying the sun’s position in the sky, should do so with caution and realize that staring directly at the sun can do irreparable damage to the eyes.Telescopes and binoculars will not protect the eyes whatsoever. One simply way to establish where the cardinal points are is to set a watch with hands at local time. Digital watches are useless for this type of observation. Locate the sun and point the hour hand at this, now point the small hand half way between the hour hand and midday (twelve o’clock). The hour hand on your watch is now pointing south.

In the northern hemisphere the sun’s arc will be located on the south side of a tree. The growth on the tree will be more healthy on the south side of the tree as well. This will be more evident on oak, beech, black and white poplars, Norway Maples and the black locust tree. On the south side of the trees one will note a slight declination. The branches on the south side of the trees will be more horizontal while those on the north side will look as if they are stretching up vertically seeking the sun. One can also look for flowering plumes which tend to grow away from the sun. Deciduous trees usually grown on the southern side of a hill in the northern hemisphere. Evergreens will be found on the northern slope. On southern slopes the heat from the sun often leaves melted shadows of trees, shrubs, stones etc.

One can find the cardinal points by using the ‘sun shadow method‘. The sun moves across the sky from east to west with its shadow gradually changing in length. This helps make this specific method work like a dream. Simply clear a flat area of dirt or sand. This works on grass but not as well as dirt or sand. Now garb a stick which is between 2-3 feet in length. Poke this into the ground so that it stands up straight. Take another stick of pebble and place this right on the end of the line of shadow the first stick makes. Wait for half an hour and the place another stick at the very end of the new shadow. Wait for another ½ hour and repat the process. The line between the two pebbles runs in an east-west direction. The first mark is west and the second is east. If you are located in the northern hemisphere, North direction will be perpendicular to the east-west line which is headed away from the sun. Therefore the south is down under.


More about this author: Janette Waldron

From Around the Web