There are several ways by which we can obtain Sun time, but all of them are based on the same principle. The way that was used by people who first began to think about these things, and it is also a good way for you to try, is like this:
Fig. 162.—Diagram Showing How to Find Solar Noon.
First you must have a good horizon, that is, you must be able to see the Sun rise and set without any mountains or other things in the way.
When you begin your observations for getting solar time note exactly where the Sun rises and where it sets on the horizon. You can easily do this by using hills, houses and trees for marking the places. Now with your eye draw a line between these two points.
Notice also where you are standing and let your line of sight meet the imaginary line which joins the places where the Sun rises and sets just as near the middle as you can, and all of which is clearly shown in [Fig. 162]. Now this line will run due north and south and hence it is a meridian line which you are to use to observe the Sun.
When the Sun reaches that point in the sky where it is directly over the middle of the imaginary line, joining the places where it rises and sets, it is exactly noon, Sun time.
The next day observe the Sun in the same way and when it crosses the meridian line again the Earth will have turned round once and you will have a part of time measured off called a Sun or solar day.
When the time is taken between two succeeding crossings of a meridian by the Sun a day so measured is called by astronomers an apparent solar day, and when the Sun is on the meridian it is called apparent noon.
Now the word apparent means to seem, that is, something which is obtained by observation. An apparent solar day is then the length of a day measured by the Sun, and while we might suppose that the Sun at least would always give a day of the same length, this is not the case for the reason that the Earth does not travel in all parts of its orbit round the Sun at the same rate of speed, and, further, it is tilted on its axis; together these things make the days as measured off by the Sun unequal and hence they are called apparent solar days.