Measuring the Sun and Moon
Timekeeping is superbly important in our modern world. It helps us make it to doctor’s appointments, schedule birthday parties, and know when to take that delicious cake out of the oven. Understandably, there are many people who insist that we would not need to keep time in a survival situation, as it would be unnecessary during a struggle for survival. However, it can be argued that in the absence of electronic clocks and cell phones or centralized timekeeping services to base our own windup clocks off of that the ability to track the time is actually even more needed during an emergency.
Timekeeping would allow you to know when the sun would rise and set, giving you the number of hours available to walk, work, hunt, and trade and it would help you to calculate cooking times to ensure that meats and baked goods are thoroughly baked and safe to eat. In the event of a total disaster, you could also use timekeeping to setup timely meetings between far flung neighbors and towns to arrange for mutual protection.
Calculating with only the Sun and Moon
When it comes to timekeeping, the more precise your tools the more precise you can be in your calculations. However, there are survival situations where you may not have access to the means to build even a rudimentary clock or sundial and will have to rely on rougher calculations based on unaided observations of the sun and moon.
Do will note that the ability to at least take notes on your calculations can keep you more consistent even if you are making rougher guesses, so try to keep some records on paper when possible. This is particularly true of moon observations, as the issue of moon phases makes nighttime calculations a little more involved even without tools for measurement.
Using the Sun
When you think of measuring time with the sun you probably think of a sundial. Although we will cover how to make one of those in part 2, here you will be applying a similar principle without the need for an actual measuring device. Rather than looking at shadows on the ground, you will need to observe the path of the sun as it travels across the sky and make a sort of “mental clock” that determines a rough hourly guess from the place the sun sits in the sky. The actual methodology is a little more complex, so let’s break it down step-by-step.
Face to the south and observe the sun’s position from that viewpoint. North America is (naturally) in the Northern Hemisphere so the measuring line of the equator is to our South. For readers in the Southern Hemisphere, you should look north instead.
Look for the place in the sky that corresponds to “high noon”, or the point where the sun is in the very center of the sky. This is 12:00 for the middle of each timezone, without compensating for Daylight Savings Time. If you are positioned to the west of your timezone’s center, “high noon” is actually later in the day, while the eastern half of the timezone has “high noon” before 12:00.
If you’re good with purely mental pictures, you can segment the sky into equal points ranging out from the center. Depending on the time of year, you’ll need to split the sky into 14 (between March and September), 12 (as you close in on the end of March or September) or 10 (between September and March) equal points, corresponding roughly to the number of daylight hours.
For most of us who aren’t readily able to make mental images of that complexity, you can use a constant physical object to measure equal points for future reference. A fist is one of the easiest things to use, and it can be quite helpful when you want to include a rough evaluation of the number of minutes left in the current hour. If, for example 2 fists equal 1 hour, then if you measure the sun and find that it fits between 2 fists, you can see that 1/2 hour, or 30 minutes have passed. Again these are obviously very rough estimates and not fit for exact timing, but they’re great when you just need to know how long the day will last or to determine when the morning heat/afternoon cooling will begin.
Separating the day out into hourly points helps you to measure the daylight hours.
Using the Moon
Obviously using the sun only works for daylight hours, and setting hourly guard shifts at night demands a timekeeper for the twilight as well. The moon is different from the sun in a number of major ways, the first and most obvious being its phases. During a new moon (when the moon cannot be seen at all), it is absolutely useless for timekeeping, which makes it less desirable. During the full moon phase, time can be calculated just as you do with the sun, since you don’t have to compensate for the way light travels across a smaller chunk of the moon like you would normally. Furthermore, it can be much more difficult to determine the moon’s hourly positioning when under heavy cloud cover, as the radiance of the moon is more easily obscured and hidden. Finally, the moon cannot always be used to measure the entire night, since it can set at different times according to its phases.
However, timekeeping via the moon is still a valuable skill, and one that requires different methodology unless you have the fortune to use the full moon in your calculations.
Find the moon and determine its phase and shape. You don’t need to have memorized a phase chart, but ideally you do want to find the moon just as it rises so you can begin determining time from that initial form.
Divide the moon in half vertically as if you could see the entire moon, then begin breaking down each half into equal pieces. Again, you eventually need 14,12, or 10 hour pieces, but reverse the seasons (i.e. summer is shorter while winter is longer).
Mentally draw a line horizontally right through the center of the moon, and then look at the part of it that is visible. Breaking the visible portion down into its hourly pieces, find the piece that touches the dark part of the moon in the center. For example, if you have a crescent moon you want to look at the center of the crescent for this measurement, not the “arms”.
If the lit portion of the moon is on the right side, then count the number of light pieces from the right edge to the point where light and dark meet along the horizontal line. This will tell you how many hours it will take for the moon to set. If you know that the moon rose at 6:00 PM, and the moon has three lit pieces before the dark side intersects, then the moon will set at 9:00 PM.
If the lit portion of the moon is on the left side, count the number of light piece from the left edge to the point where light and dark meet along the horizontal line. In this case, this will tell you how long you have until dawn. If the moon rose at 4:00 AM and there are three light pieces on the left side, you will see the sun rising at 7:00 AM.
Divide the moon’s path into 14,12, or 10 equal points corresponding to the season. We will use the information you gathered in steps 4 and 5 along with the hourly path of the moon to determine time. We had to add the previous step since the moon doesn’t have a “high noon” to measure from.
Using your knowledge of when the moon should rise and/or set, determine where it is currently positioned along your hourly points. For example, if you know that the moon rose at 6:00 PM and should descend at 12:00 AM, then if the moon is in the center of its arc it is currently 9:00 PM. If you know that the moon rose at 4:00 AM and morning should begin at 8:00 AM, a moon 3/4 along its arc of travel would indicate 6:00 AM.
Although this is more for artistic beauty than practical separation, it does give an idea for you how can separate the moon’s travel into hourly segments just like the sun.
With these two methods you will be able to get a rough guess of all the daytime hours and most of the nighttime hours depending on your season. This is another one of those skills that require a little thought to master initially, but can become almost second nature after awhile. Learn now when you have the luxury of perfecting your technique against guaranteed timepieces so that you’ll have finely honed natural timekeeping skills once the lights go out!
2 Methods for Building a Temporary Sundial
We delved into timekeeping by observing the travels of the sun and moon across the sky. We also found that there were definite limitations and imperfections to those methods, owing to a lack of definite measuring tools to determine the time.
We’re going to take a look at the next step from simple mental figuring and start using a few simple tools in order to measure time more accurately with a sundial.
Sundials: the Pre-Mechanical Clock
Sundials were among the first ways ancient peoples could quickly and easily measure time in an accurate manner. Not only that, but a sundial was also something that multiple people could use and come up with the same time, since just looking at the sun or moon could leave internal clocks off by an hour or two. A key advantage that we as preppers love is of course the lack of electricity or complicated moving parts. A sundial is, at its core, just a stick in the center of a circle with small notations for various hours and minutes. A few pebbles to mark the circle and a piece of wood can make a crude but effective clock, even in your own backyard! However, a few simple tricks can improve the sundial greatly and give you much better accuracy.
Why Not a Permanent Sundial?
Before we get into building your “sun clock”, let me point out the two reasons why these are not designs for a permanent sundial.
A permanent sundial requires that you move the stick or rock that casts the shadow based on the month if you want true accuracy month-to-month. Lacking a chart to tell you where to move your stick, it would be difficult to compensate with a simple “stick and pebbles” design.
You would need stronger and more durable materials to ensure that the clock wasn’t marred in some way. Even a light rain that causes the stick to sink a little bit in the mud could throw off the calculations, as could a strong wind. A truly permanent sundial would be constructed of rock or metal, with mechanisms in place to allow you to keep the shadow-casting rod firmly immovable until the change of the month.
A stone or metal sundial is needed for true permanency.
These designs are meant to be built with minimal input required, and to be used for a few weeks at most. They can be built at a retreat or even when bugging out, making the designs extremely portable as well. As with any temporary or makeshift tool, you should take their limitations into consideration when making use of them.
A Simple Dial Excellent for Determining Time when Bugging Out
This design is much easier to implement, requiring less data and mathematical skill to use, but is also less precise. I’d recommend this for quick calculations and for when you’re moving often (bugging out, hunting for weeks at a time etc).
Clear a reasonably flat area of ground where you can place your sundial. Obviously make it a place where sunlight is consistent and you won’t have shadows interfering with the sundial’s functioning as much as possible.
Find true north, then stick a footlong stick into the ground and orient it towards that direction. This stick (or gnomon) will be the piece that casts a shadow for your sundial. If you have a properly calibrated compass this is easy, but you can also use your gnomon to determine it if you wish. Simply place stones where the tip of the shadow from your gnomon meets the earth until you’ve made a nice half circle over the course of a day. True north will be where the shadow was shortest throughout the day, or where the closest pebble was placed. If you plan on making multiple sundials in the same general area, it will be helpful to make a mark to determine where truth north is for future sundials so that you can skip the day-long wait.
Place a pebble 2 inches to the north of your stick, to mark 12:00 Noon.
Two inches south of the gnomon, draw a line 2 feet long, one foot on either side of the gnomon. The stick should be in the exact center of 2 foot long lines.
Kneeling behind this line facing north, place a pebble on each end of the line.
Place 5 pebbles on either side of the 12:00 pebble from step 3, spacing them evenly apart. These will mark the hours for you.
Your simple sundial is complete and ready for calculations.
If you can, I would recommend practicing this several times with a watch handy, so that you can get better at judging the distances of the stones, the angle of the gnomon stick, etc. This will serve you well in almost any environment with sufficient sunlight for a sundial clock to be used.
How to Construct a Much More Precise Temporary Sundial?
This is more complex to construct, requiring some math, knowledge of how to draw an ellipse from major and minor axes, and knowing how to find your current latitude, but it is also very accurate considering it’s made of sticks and pebbles. Not really suitable for bugging out, I’d recommend this for use in a retreat when you don’t have the time/materials to construct a permanent sundial.
Clear a reasonably flat area of ground where you can place your sundial, and place your stick in the center of where you would like your circle to be. Depending on your needs a sundial can be as large as you want, based on the size of the center stick (or gnomon) and the precision you want. Obviously it is easier and more precise when measuring time if the shadow is fairly close to the edge of the circle, but you could have a tiny 3 inch high stick for a football field sized circle if you wanted.
Find true north and draw a line that goes from north to south that passes through the spot where you placed your gnomon. As with the simpler dial above, If you have a properly calibrated compass this is easy, but you can also use your gnomon to determine it if you wish. Simply place stones where the tip of the shadow from your gnomon meets the earth until you’ve made a nice half circle over the course of a day. True north will be where the shadow was shortest throughout the day, or where the closest pebble was placed. If you plan on making multiple sundials in the same general area, it will be helpful to make a mark to determine where truth north is for future sundials so that you can skip the day-long wait.
Draw another line that goes east to west, perpendicular to the north/south line. This will make a small + right in the center of your circle.
Draw the circle, with the gnomon and the + you drew in the center. Again, although you can make it any size you want it works best if the tip of the shadow just touches the edge of your circle.
Extend the + lines through your circle. This will be helpful later.
Make a mark with a pebble every 15 degrees in your circle. To do this, simply draw a line that splits Northeast/west and Southeast/west right in half, which will leave you with 8 pieces of your sundial “pie”. Then split each of those chunks into 3 equal pieces until you have 24 equal pieces around your circle. Since a circle is 360 degrees, and 24 times 15 equals 360, this will give you 15 degree marks around the entire circle.
Determine your approximate latitude, and mark that location with a pebble on your circle. If you have a map with latitude/longitude lines on it this task will be simple, but if you lack for it there is one simple method using the North Star. If you are in the Northern Hemisphere, you can find the North Star at the end of the handle of the Little Dipper, then measure how many degrees above the horizon the star is, which is also what latitude you are in. If you have a multiple of 15 (15, 30, 45 etc) as your latitude, just use a pebble you’ve already had marking the degrees for your circle.
Draw a perpendicular line from your latitude pebble towards the North/South line. This will make another intersection, which will form the basis for an ellipse described in the next step.
Starting at the point where your latitude stone line and the North/South line intersect for the minor axis, draw an ellipse with the intersection of your circle from step 4 and the East/West line as your major axis. Since the exact way to draw an ellipse would take several steps to detail here, see this link to determine how to draw an ellipse using the circle and two axes given.
Draw a line extending straight north or south from each of the 15 degree pebbles until they intersect the ellipse. These intersections will mark the hours for you.
You will need to correct for your longitude depending on whether you are east or west for your timezone. Each timezone is a multiple of 15 in longitude, since each one marks out an hour’s time difference: Pacific time is 120 degrees, while eastern time is 75. For each degree west of your timezone’s longitude, you are 4 minutes ahead, while each degree east leaves you 4 minutes behind what your sundial tells you.
Your sundial is, at last, ready for service.
As you can see, this second method can be rather difficult to put together the first few times, so I would strongly recommend practicing to work the kinks out while you have watches and cell phones to compare your handiwork to.
Now you have multiple tools at your disposal for telling time, and the ability to make use of them. Practice your methods of choice, and be ready for a world without electrical clocks!