Your rudder steers your vessel but your compass guides your vessel!
What would you do if your compass dies? The compass could fall overboard, get affected by strong magnets, or even spring a leak and lose all its fluid. Now what?!
With paper charts, you can run out your Dead Reckoning line to see what area of the world you are heading towards if you don’t alter course; but you still need a way to make sure you are staying on a course.
By day, you have the Sun to use for navigation. By night you have the stars to guide you in the darkness of the open ocean.
The Sun rises in the East and sets in the West, roughly. Throughout the seasons there are some declination fluctuations since the Earth spins on a tilted axis. This means that the Sun will rise and set slightly South of East and South of West if you are in the Northern Hemisphere, and slightly North of East and North of West if you are in the Southern Hemisphere. Suddenly, using it as a guide begins to fail as an idea.
With an analogue watch, you can roughly figure out which way is North and South, but you are going to need some help. On land, where watches are set according to local time, all you have to do is pull out your watch and look at it. The problem is that you are out at sea, traveling across timezones, so your watch is no longer set to “local” time. Your first step will be to figure out what time is “local”.
You will need to sit around and observe the shadows on your boat. Preferably look at the shadows of your stanchions or some other small pole on your deck. You want to keep track of the shadow it casts, as the shadow will tell you which way is North at that instant and when “Noon” occurs to set your watch to.
As the sun rises and makes its way to the highest point in the sky, the shadow of such a component on your deck will begin to shorten. At it’s shortest, the shadow will be pointing North (opposite if you are in the Southern Hemisphere) and the moment when the shadow is shortest is “Noon”.
This sounds simple in theory, but it will be tricky to do and your measure of “Noon” will be rather rough since the boat is going to be moving around in the seas. If you happen to have a sextant, this measure of noon will be much more precise because you can use the sextant to find the highest position of the sun in the sky! If you had a sextant though, you wouldn’t need all these other methods because you would already be navigating!! Moving on…
You guess roughly what time is noon with your shadow trick and now you have a lowly calibrated watch that tells you the cardinal directions and is not on time with any other watch in the world! Using the watch, you can point the hour hand at the sun and look at the face of your watch. Now draw an imaginary line that bisects the angle between the hour hand and “12” on the face. If you are in the Northern Hemisphere, the bisecting line will point South and the opposite position on the watch face will point North.
If you are in the Southern Hemisphere, the opposite will be true and the line between the hour hand and “12” will be your North and the opposite side of the face will be South.
Let’s try this out in the Northern Hemisphere. It’s 6AM and the sun just came up over the horizon. You point the hour hand at the sun and look at the face.
Three points are going to be told on the face: Sun is at “6”, “12” is directly opposite so “9” will be pointing South, while “3” will be pointing North.
Now it’s 10AM and the sun is higher in the sky. Sun is at “10” “12” is much closer to the hour hand, “11” will be pointing South as it is the bisecting point on the face between the hour hand and “12”, therefore “5” is North.
At Noon, the Sun is at “12” and so is “12”, so “12” is South and “6” is North.
At 5pm, the Sun is starting to get low to the horizon. Sun is at “5”, “12” is now farther from the hour hand and “2:30” (halfway between 2 and 3) will be pointing South and 8:30 will be pointing North.
This is a cool parlor trick, but if you are sailing East or West, you will have to recalibrate your watch for the new “noon” as you will be traveling across timezones and your timely compass will begin to waver in accuracy.
Why does this work? It’s rather simple actually. If you are in the Northern Hemisphere (and not too close to the equator as during the summer, the sun actually comes over the equator which would then put you into the “Southern Hemisphere Setting” even though you are still in the Northern Hemisphere) the sun will rise in the East, set in the West, and transit the sky South of your position. At any point in the day, if you are looking in the direction of the sun you are also looking in a Southern direction. At Local Apparent Noon, the Sun will be directly South of you and any shadow cast will point due North. Therefore, as the sun rises, by tracking it with the hour hand which moves along the face of the watch at the same speed as the sun moves across the sky, you can track it’s position. Since the sun will be South of you at Noon, when the hour hand is at “12”, the angle between the hour hand and “12” will be 0 and “12” will be pointing South while “6” will be pointing North.
This lets you track the day and the sun to maintain your moving compass rose that floats around the face of the watch relative to the hour hand and “12” position.
The end result is a crude compass that will allow you to maintain a relative course without steering in circles.Now, if these concepts are familiar to you then you probably already understand the relationship between the Sun, time, and your position on the Earth. You might lose your compass, but you definitely still have your sextant secured in a safe place because the Sun is your guide and you already understand how and why a Noon-sight works.
