How to make a sundial your own. Sundial at the dacha. DIY sundial

Hello, dear readers of KARTONKINO.ru! Spring... Somewhere it is already in full swing, somewhere they are just waiting for its arrival, in a month or two, but everywhere the sun shines brighter and longer. And we have a great opportunity to put sunlight to work by making sundial with your own hands. Of course, they will not replace traditional - mechanical and electronic - watches, but this homemade product is very entertaining, and for representatives of the younger generation - also educational, because the model of the sundial that we will make is the most effective one, and its manufacturing will require certain knowledge in the field of astronomy and trigonometry.

There are many varieties of this ancient device for measuring time. But among all the variety of sundials ever used, the following types are distinguished as the main or classic ones:

— equatorial(in such a sundial, the plane of the frame (dial) is parallel to the equator, and the gnomon (the part that casts the shadow), usually a metal rod, is parallel to the earth’s axis);

Equatorial sundial on the banks of the Thames (London, England)

— horizontal(the plane of the frame is parallel to the horizon plane, and the gnomon has the shape of a triangle, one of the sides of which is inclined to the plane of the frame at an angle equal to geographical latitude clock installation location);

Horizontal sundial (Limassol, Cyprus)

— vertical(as the name suggests, the dial of such a watch is placed in a vertical plane, usually on the walls of buildings).

Wall sundial (Ely Cathedral, England)

We will make an equatorial type sundial, as it is the easiest to make. Due to the fact that the dial is installed parallel to the equator, and the sun moves almost uniformly across the celestial sphere, the shadow of the gnomon will shift by an angle of 15° every hour. Therefore, the hour divisions on the dial are applied in the same way as in regular watch, only the marks needed are not 12, but 24. It is clear that top part The dial is unlikely to be useful, except for residents of the Arctic, when the polar day comes and the sun will shine around the clock.

There is no need to draw the dial yourself, you can use ready-made templates- round or square (whichever you prefer):

Our task comes down to correctly orienting the sundial in space. The angle of inclination of the dial relative to the horizontal plane is determined as follows:

α=90°-φ ,

where φ is geographical latitude. You can find out the latitude of your place of residence on a map or on Wikipedia.

And knowing the necessary angles, it is very simple to make an inclined stand for our sundial from cardboard or paper and then stick a printed dial on it or prepare a scan of the watch case with a printed image of the dial in a graphics editor.

We know the dimensions of the dial template. The side of the body is right triangle. Thus, we know the length of the hypotenuse C and the angles of the triangle, and the lengths of the legs A and B are calculated by trigonometric formulas:

A=C×sinα

B=C×cosα

All that remains is to draw the development according to the obtained dimensions, it is possible even without the side walls.

I made a case with an opening back cover (I’ll explain why below):

No matter what you do, you still end up with a box.

Well, now you need to install a gnomon in the center of the dial. To do this, you can use any rod of suitable size (for example, plastic straw from a juice bag). You can also make it from cardboard or paper:

— cut out a rectangular strip 60 mm wide (we determine the length empirically, by eye, so that when folded, you get a dense tube with a diameter of about 5-6 mm with a small hole);

— glue double-sided tape to one edge and roll up the tube;

— cut out another rectangular strip 15-20 mm wide and also roll it into a tube with a diameter that matches the diameter of the hole in the first tube;

- cut off part of the first tube at a distance of 10 mm from the edge (this will be something like a nut)

and connect the parts;

— we fix the gnomon on the dial, fixing it on the reverse side with a “nut” (this is where the opening lid comes in handy).

The sundial is ready. Now, for them to work correctly, you need to place them in a sunny place (on a windowsill, on a balcony, etc.) so that the gnomon “looks” north (we determine the direction using a compass).

Of course, you should not expect an exact coincidence of the readings of such a sundial with the readings of ordinary watches. First, a sundial showing the true solar time, do not take into account standard time in a particular area. Secondly, we should not forget that the magnetic and geographic poles of the Earth have a discrepancy, and the fact that we oriented the watch along the magnetic pole will also introduce some error.

And finally, the main point that you also have to take into account is that the equatorial clock only works during the period between the days of the spring and autumn equinox. The rest of the time, the upper surface of the frame will be in the shadow. But the day of the spring equinox in the northern hemisphere is soon, so the wait will not be long. There is just enough time to make a sundial with your own hands and set it up to work.

Successful experiments to you!

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By the way, a new master class on making a sundial is already ready. This time we are talking about a horizontal type pocket watch model.

See you again in KARTONKINO!

DIY sundial. Master Class

Spring... It's already in full swing... The sun shines brighter and longer everywhere. And we have a great opportunity to put sunlight to work by making a sundial with our own hands. Of course, they will not replace traditional - mechanical and electronic - watches, but this homemade product is very entertaining, and for representatives of the younger generation - also educational, because the model of the sundial that we will make is the most effective one, and its manufacturing will require certain knowledge in the field of astronomy and trigonometry.

There are many varieties of this ancient device for measuring time. But among all the variety of sundials ever used, the following types are distinguished as the main or classic ones:

Equatorial (in such sundials the plane of the frame (dial) is parallel to the equator, and the gnomon (the part that casts the shadow), usually a metal rod, is parallel to the earth's axis);

Equatorial sundial on the banks of the Thames (London, England)

Horizontal (the frame plane is parallel to the horizon plane, and the gnomon has the shape of a triangle, one of the sides of which is inclined to the frame plane at an angle equal to the latitude of the place where the clock is installed);

Horizontal sundial (Limassol, Cyprus)

Vertical (as the name suggests, the dial of such a watch is placed in a vertical plane, usually on the walls of buildings).

Wall sundial (Ely Cathedral, England)

We will make an equatorial type sundial, as it is the easiest to make. Due to the fact that the dial is installed parallel to the equator, and the sun moves almost uniformly across the celestial sphere, the shadow of the gnomon will shift by an angle of 15° every hour. Therefore, the hour divisions on the dial are applied in the same way as in a regular watch, only the marks need not 12, but 24. It is clear that the upper part of the dial is unlikely to be useful, except for residents of the Arctic, when the polar day comes and the sun will shine around the clock.

There is no need to draw the dial yourself; you can use ready-made templates - round or square (whichever you prefer):

Print the dial-square template

Print the dial-circle template

Our task comes down to correctly orienting the sundial in space. The angle of inclination of the dial relative to the horizontal plane is determined as follows:

Where φ is geographic latitude. You can find out the latitude of your place of residence on a map or on Wikipedia.

We know the dimensions of the dial template. The side of the case is a right triangle. Thus, we know the length of the hypotenuse C and the angles of the triangle, and the lengths of the legs A and B are calculated using trigonometric formulas:

All that remains is to draw the development according to the obtained dimensions, it is possible even without the side walls.
I made a case with an opening back cover (I’ll explain why below):

No matter what you do, you still get a box.

Well, now you need to install a gnomon in the center of the dial. To do this, you can use any rod of suitable size (for example, a plastic straw from a juice bag). You can also make it from cardboard or paper:
- cut out a rectangular strip 60 mm wide (we determine the length empirically, by eye, so that when folded, you get a dense tube with a diameter of about 5-6 mm with a small hole);

- glue double-sided tape to one edge and roll up the tube;

- cut out another rectangular strip 15-20 mm wide and also roll it into a tube with a diameter that matches the diameter of the hole in the first tube;

- cut off part of the first tube at a distance of 10 mm from the edge (this will be something like a nut)

and connect the parts;

- fix the gnomon on the dial, fixing it on the reverse side with a “nut” (this is where the opening lid comes in handy).

Of course, you should not expect an exact coincidence of the readings of such a sundial with the readings of ordinary watches. Firstly, sundials that show true solar time do not take into account the standard time in a particular area. Secondly, we should not forget that the magnetic and geographic poles of the Earth have a discrepancy, and the fact that we oriented the watch along the magnetic pole will also introduce some error.

And finally, the main point that you also have to take into account is that the equatorial clock works only during the period between the days of the spring and autumn equinox. The rest of the time, the upper surface of the frame will be in the shadow. But the day of the spring equinox in the northern hemisphere is soon, so the wait will not be long. There is just enough time to make a sundial with your own hands and set it up to work.

Successful experiments to you!

And we have a great opportunity to put sunlight to work by making DIY sundial. Of course, they will not replace traditional - mechanical and electronic - watches, but this homemade product is very entertaining, and for representatives of the younger generation - also educational, because the model of the sundial that we will make is the most effective one, and its manufacturing will require certain knowledge in the field of astronomy and trigonometry.

There are many varieties of this ancient device for measuring time. But among all the variety of sundials ever used, the following types are distinguished as the main or classic ones:

Equatorial (in such sundials the plane of the frame (dial) is parallel to the equator, and the gnomon (the part that casts the shadow), usually a metal rod, is parallel to the earth's axis);

Vertical (as the name suggests, the dial of such a watch is placed in a vertical plane, usually on the walls of buildings).

Wall sundial (Ely Cathedral, England)

We will make an equatorial type sundial, as it is the easiest to make. Due to the fact that the dial is installed parallel to the equator, and the sun moves almost uniformly across the celestial sphere, the shadow of the gnomon will shift by an angle of 15° every hour. Therefore, the hour divisions on the dial are applied in the same way as in a regular watch, only the marks need not 12, but 24. It is clear that the upper part of the dial is unlikely to be useful, except for residents of the Arctic, when the polar day comes and the sun will shine around the clock.

There is no need to draw the dial yourself; you can use ready-made templates - round or square (whichever you prefer):

Our task comes down to correctly orienting the sundial in space. The angle of inclination of the dial relative to the horizontal plane is determined as follows:

α=90°-φ ,

where φ is geographical latitude. You can find out the latitude of your place of residence on a map or on Wikipedia.

A=C×sinα

B=C×cosα

All that remains is to draw the development according to the obtained dimensions, it is possible even without the side walls.

I made a case with an opening back cover (I’ll explain why below):

No matter what you do, you still end up with a box.

We cut out a rectangular strip 60 mm wide (we determine the length empirically, by eye, so that when folded, we get a dense tube with a diameter of about 5-6 mm with a small hole);

Place double-sided tape on one edge and roll up the tube;

We cut out another rectangular strip 15-20 mm wide and also roll it into a tube with a diameter that matches the diameter of the hole in the first tube;

Cut off part of the first tube at a distance of 10 mm from the edge (this will be something like a nut)

and connect the parts;

We fix the gnomon on the dial, fixing it on the reverse side with a “nut” (this is where the opening lid comes in handy).

Successful experiments to you! And see you again at

A typical gnomon in its original form

It is also customary to call a gnomon the part of a sundial that casts a shadow on the dial.

Gnomonics is the science that studies sundials. Today, gnomonics is nothing more than a scientific hobby, since more accurate and easy-to-use instruments have been created to determine the true meridian and time.

Theoretical information

Let us list some facts based on knowledge of astronomy that will help you understand the principle of operation of the gnomon.

Fact No. 1. The sun always moves from east to west, which means the shadow from the gnomon moves in the opposite direction, that is, from west to east.

Fact No. 2. During sunrise and sunset, when it is directly above the horizon, the shadow from the gnomon is the longest, and at solar noon it is the shortest.

Fact No. 3. The shortest shadow from a gnomon is obtained when the Sun is at its zenith, that is, the highest point of its trajectory across the sky. At this moment, the Sun crosses the true meridian, that is, the line connecting north to south.

Fact No. 4. The fastest change in shadow length is observed during the hours of sunrise and sunset over the horizon. In the middle of the day, the rate of change in shadow length is minimal.

Fact No. 5. Due to the inclination of the Earth's rotation axis relative to the plane of the Earth's orbit at an angle of approximately 23.5 degrees, as well as due to the rotation of the Earth around the Sun, the observed movement of the Sun across the sky occurs below the celestial equator (in the northern hemisphere from September to March) , then above it (in the northern hemisphere from March to September). And only on the days of the spring and autumn equinoxes does the movement of the Sun coincide with the plane of the celestial equator. Moreover, the trajectory of the Sun's movement lies farthest from the celestial equator on the days of the winter and summer solstices.

By the way, the celestial equator is a large circle of the celestial sphere located perpendicular to the Earth’s axis of rotation, the plane of which coincides with the plane of the Earth’s equator.

Fact No. 6. The sun moves across the sky with angular velocity approximately equal to 15 degrees per hour.

Fact No. 7. Average “terrestrial” time does not always coincide with astronomical time for a number of reasons.

Fact No. 8. The diameter of the Sun visible from Earth is approximately thirty arcminutes. This makes the shadows of objects blurry.

Fact No. 9. If you stand in such a way that the north is in front of your face, then the south will be behind you, the east will be on your right, and the west will be on your left.

Understanding the processes underlying the operation of the gnomon and sundial is necessary not only in order to make these devices yourself, but also in order to use them correctly. Once I happened to observe a funny picture: a man, having bought a sundial, could not understand why the time on it and on the clock on his phone was different. The video shows this example:

How to use a gnomon to determine the true meridian

The gnomon in this case is a pillar, column or other straight vertical object located on a flat horizontal area open to the Sun. It is believed that increasing the length of the gnomon will increase the accuracy of measurements, since in this case changes in the length of the shadow become more noticeable. However, do not forget that as the length increases, the clarity of the cast shadow will decrease, which can negatively affect the accuracy of measurements. Also, the accuracy of the results is affected by the thickness of the upper part of the gnomon, which is why it is often made pointed.

On a clear sunny day, the shortest shadow from the gnomon indicates the onset of astronomical noon and points north (in the middle and high latitudes of the northern hemisphere) and south (in the middle and high latitudes of the southern hemisphere). In the tropics and at the equator, the situation can change throughout the year, as we have discussed in detail here.

Thus, by the shortest shadow it is possible to determine both true noon and the direction of the true meridian. Among other things, knowing the height of the gnomon (B) and the length of the shadow (L), it is not difficult to calculate angular height(H) The sun is above the horizon. To do this, use the formula tgH=B/L.

However, due to the slight change in the length of the shadow from the gnomon during lunch hours, it is not always possible to accurately determine the shortest shadow. If you need to obtain more accurate results, you can use another method. To do this, determine the bisector between two identical shadows of the gnomon, measured in the morning and evening time, when the rate of change in shadow length is more significant. It is this method that underlies one of the methods of orientation by the shadow of the Sun.

Knowing the true meridian, you can easily navigate the area by determining the direction north or south, and then all other cardinal directions.

How to use a gnomon to determine the latitude of an area

In addition to determining the true meridian, using a gnomon you can approximately calculate the latitude of the area in which measurements are taken. Next, we will consider several methods that arise from knowledge of astronomy.

Method number 1. On the day of the autumn or spring equinox at true noon, the angular altitude of the Sun is determined using the previously discussed formula. The resulting value is subtracted from 90 degrees. The result of the calculations will be the latitude of the area.

Method number 2. On the day of the winter solstice at true noon, the angular altitude of the Sun is determined. Since at this moment the Sun is below the celestial equator at an angle equal to the angle of inclination of the earth’s axis, that is, 23.5 degrees, then by adding this angle to the angular height of the Sun obtained from the formula, we can obtain the angular height of the celestial equator. When subtracting the height of the celestial equator from 90 degrees, a value corresponding to the latitude of the area is obtained.

The movement of the Sun across the sky in summer time in high latitudes.

This method can also be used on the summer solstice. To do this, you need to subtract 23.5 degrees from the angular altitude of the Sun to obtain the angle of inclination of the celestial equator, and knowing the angle of inclination, the latitude of the area.

The movement of the Sun in high latitudes in summer, when it does not set beyond the horizon.

Method No. 3. At true noon, shadow length measurements are taken daily. As a result of these measurements, you need to get the longest or shortest shadow, which will correspond to the winter or summer solstice, respectively, and then proceed according to the second method. Or, having determined the longest and shortest shadow, find the average length value, calculate the angular height of the Sun using the formula, focusing on the obtained average value, and act in accordance with the algorithm of the first method.

When obtaining results using one of the above methods, it should be remembered that the apparent height of the Sun above the horizon is to some extent influenced by the effect of light refraction - refraction, which we talked about here. Because of this effect, all celestial bodies may appear higher than where they actually are located. And the more pronounced this effect will be, the closer to the horizon the observed object is located.

It follows from this that near the poles on the days of the spring and autumn equinoxes, when the Sun passes low above the horizon, the measurement results may differ slightly from the real ones towards lower latitude.

Now let's look at how to determine the time and date using a gnomon.

Gnomon and sundial

A sundial is an ancient instrument that allows you to determine time by the shadow of the Sun during daylight hours.

One of the very first sundials appeared in Egypt. They were a stone block approximately 30 cm long. This block was located along the east-west direction. On one side of this clock there was a “T”-shaped block, the shadow from which, decreasing, “crept” along the block from morning to noon, after which the sundial was turned 180 degrees and the shadow “crept” in the opposite direction. The time was determined by the notches made on the block.

Sketch of an "Egyptian" sundial.

The very first notes about sundials are found in Egyptian manuscripts and date back to 1306-1290 BC. The discovered Egyptian sundial, according to scientists, was made long before the found manuscripts describing them - back in 1479-1425 BC.

One of the first sundials.

Other models of ancient sundials were also discovered in Egypt, different from the model described, but their age, according to the testimony of scientists, is younger, so it is not necessary to consider them as the most ancient sundials.

Reconstruction of an ancient sundial in Egypt, exhibit of the Cairo Museum.

Regardless of Egypt, sundials appeared in other parts of the world, for example, ancient China and in Ancient Greece, from where their idea migrated to Ancient Rome.

In Rus', cathedral towers that cast shadows began to be used as sundials. But all this was already practiced in the 11th century AD.

However, such a watch could not show exact time, since the notches were made by uniformly dividing the scale into a fixed number of parts.

And only many centuries later, humanity came up with a sundial that showed more accurate time. They were more similar to modern analog watches, with the only exception that their scale was designed only for a period of time from morning to evening and looked more compressed.

Such sundials can still be found today: it has become fashionable to decorate squares with them. Sometimes sundials can be found on garden and summer cottages, where they can look good at the intersection of paths.

Sundial as a decorative element.

The gnomon is an integral part of the sundial. It is he who casts a shadow on the dial, forming the “arrow”.

You need to understand that a sundial can show both astronomical and average “terrestrial” time: it all depends on the markings when constructing them. Therefore, when creating homemade watch We need to decide in advance what time we want to see on such a watch.

In addition to the time, the sundial can also show the date and month. To do this, additional markings are applied to them.

It is important to understand that such watches can correctly indicate the date and month only if they are “calibrated” strictly for specific place installations.

But there is no need to place high hopes on a homemade sundial: due to a number of inaccuracies associated with the design of the clock, the unevenness of the surface for installation, the orientation of the clock in space, the angular diameter of the Sun, the equation of time and other factors, one cannot expect particularly accurate readings from such clocks .

Let's look at several basic models of sundials that you can construct with your own hands from wood, plastic or cardboard.

Equatorial sundial

This sundial got its name because the plane of its dial is parallel to the plane of the celestial equator.

The tilt of the scale of these watches is required so that even the Sun standing at full zenith casts a shadow.

It is advisable to make such a watch in the form of a flat circle, in the center of which a gnomon is stuck, and in such a way that one part of it rises on one side of the dial, and the other sticks out on the other. If this is not done, then from September to March (in the middle and high latitudes of the northern hemisphere) you will not be able to use such a watch, because the Sun will drop below the celestial equator, which means the upper part of the watch will no longer be illuminated by its rays.

The equatorial clock is set so that the gnomon in relation to the horizon is raised at an angle corresponding to the latitude of the area, and points to geographic north. In this case, the plane of the dial will be parallel to the plane of the celestial equator.

There is often a recommendation to set a sundial using a compass. However, this often creates an additional error, since the geographic north does not always coincide with the magnetic north, which is indicated by the magnetic compass needle, which was described in detail in. In addition, an additional error in this case may arise due to various magnetic deviations.

From the point of attachment of the gnomon to the dial in the northern direction (for middle and high latitudes of the northern hemisphere), a straight line is drawn along the dial. The shadow of the gnomon will cross this line at true (astronomical) noon.

Using a protractor or any other in an accessible way Other divisions are also applied to the dial in the form of rays with the center at the place where the gnomon is attached. The angle between adjacent “rays” should correspond to 15 degrees - it is this angular distance, as we remember, that the Sun, and accordingly the shadow, travel in one hour.

The number “12” is placed above the central marking corresponding to noon. Rays located to the west are numbered reverse order, that is, “11”, “10”, “9” and so on, and the rays located to the east are numbered in ascending order, that is, “13”, “14”, “15” and so on. The result is a dial.

A similar scale is made on the bottom of the clock.

Such a clock can be quickly made from a protractor, but in this case, instead of the numbers corresponding to the hours, you will need to use corner marks. Thus, a mark of 90 degrees will correspond to 12 o’clock in the afternoon, and for each hour the shadow of the gnomon will shift either in one direction or the other by 15 degrees, from which it can be concluded how much time has passed or should pass for the “arrow” to be on 90 degrees, that is, it made it clear that it was noon. This is not very convenient, but it will take a minimum of time to build such a sundial.

By the way, in the area of the equator such a watch will stand vertically, like a wheel. And at the poles - horizontally, like a top during its rotation.

The video shows how such watches are made by hand:

Despite the simplicity of the design, such watches have a drawback: they are difficult to use on days close to the spring and autumn equinoxes, since the plane of the Sun's movement across the sky in this case is parallel to the plane of the dial of the equatorial sundial.

When turning to numerous Internet sources, I came across information that equatorial sundials cannot work on the specified days, and I never came across information on how to determine the time in these cases. Therefore, I will share my thoughts. In fact, everything is simple: you need to make a small side protruding above the surface on the side of the dial opposite to the direction of the Sun. On this side the shadow of the gnomon will be visible even on the days of the equinox.

Equatorial sundials are convenient for their versatility, since they will work anywhere on the Earth on a clear sunny day. However, it will be difficult to determine the date and month with their help due to the too long shadow and limited dimensions of the dial. But the calendar function is easily handled by a horizontal sundial, which we’ll talk about later.

Horizontal sundial

In a horizontal sundial, the dial is positioned horizontally. The gnomon in this case, by analogy with the equatorial clock, is located in the northern (for middle and high latitudes of the northern hemisphere) direction at an angle to the horizon equal to the latitude of the area.

Antique copper sundial on a fortress wall at St Michael's Mount, Cornwall, UK.

Such sundials are also located strictly according to the geographical cardinal directions.

The mark on the dial corresponding to 12 o'clock in the afternoon is made by analogy with the previous version of the sundial. At the moment of crossing the shadow of the gnomon of this mark, the time is recorded on an ordinary clock. After this, exactly an hour later the next note is made. And so on until the Sun disappears below the horizon. All marks are connected by straight lines to the location of the gnomon - a kind of ray is obtained.

The rays corresponding to the morning hours are drawn on the dial as a mirror image of the evening ones. Next, each ray is numbered by analogy with the previous version of the sundial.

You can also make marks on this dial to determine the date. For this:

On the day of the summer solstice, during the day, every hour, marks are applied to the dial, corresponding to the end of the shadow of the gnomon.
The marks are connected by a smooth curve.
The date and month on which the notes were made are signed next to the resulting curve.
Similar actions are repeated exactly a month later and so on until the day of the winter solstice arrives.
WITH opposite side Dates and months corresponding to the period from December to June are plotted on the curves. So, July will correspond to May, August to April, September to March, October to February, and November to January.

In order to approximately determine the date from such a clock, you need to look at which curve the end of the gnomon's shadow is on or between which curves, and then use the interpolation method to determine the approximate date and month. To do this, of course, you need to know at least what period the measurement is being taken, because, for example, on November 21 the shadow will be approximately the same length as on January 21.

Vertical sundial

A vertical sundial, as the name suggests, has a vertical dial. Such a dial is often attached to a pillar or wall of a building. However, it should be noted that for convenience, such a dial should be positioned strictly south (for middle and high latitudes of the northern hemisphere) or strictly north (for middle and high latitudes of the southern hemisphere).

Moscow region, facade of the Temple of Seraphim of Sarov, vertical sundial made of Inkerman limestone. The size of the plate is 100x50 cm.

The gnomon in this case, as in the previous one, should be inclined at an angle relative to the horizon equal to the latitude of the area where the sundial is installed.

The markings of the dial and calendar in this watch are carried out similarly to a horizontal sundial.

The main disadvantage of vertical sundials is the impossibility of using them in the tropical and equatorial zones, when the position of the Sun at noon shifts from north to south or vice versa. In this case, you can proceed by analogy with the equatorial sundial, making their dial reversible. However, you won’t be able to use a calendar with this watch because the gnomon’s shadow is too long.

In fact, at the equator, a vertical sundial is a special case of an equatorial sundial, since here the plane of its dial is parallel to the celestial equator, and the gnomon is perpendicular to this plane.

Converting astronomical time to local time

In order to find out “earthly” time, knowing the astronomical time determined by a sundial, you need to take into account two main points: the longitude of the area where time is measured, and the equation of time. We talked about why this is important and how it affects the difference in time readings on regular and sundials here.

In order to correct for the first moment associated with longitude, you need to remember that the Earth rotates around its axis at an angular speed of approximately 15 degrees per hour. Thus, it is possible to determine the difference between astronomical time in this area and astronomical time in the prime meridian, that is, Greenwich.

To take into account the correction associated with the equation of time, you need to have a table or graph of the equation of time. It is convenient to apply it directly to the sundial in a place where it will not interfere with other measurements.

This graph shows how much earlier or later than 12 “earthly” hours on a given day the Sun will be at its zenith, that is, it shows the difference in astronomical and “earthly” time on a given day at the “average” longitude by which the time zone is determined.

By correcting for longitude and the equation of time, you can get Greenwich “earthly” time. And knowing Greenwich time and your time zone, it’s easy to calculate the local “earthly” time.

Of course, you can go the other way, without trying to calculate Greenwich time, but then you will have to focus on time zones, which do not always clearly correspond to astronomical readings due to the political component, and therefore the explanation will be more confusing.

In this regard, let’s look at the previously mentioned algorithm using an example.

The measurements are carried out on an area with a longitude of 32 degrees 30 minutes east longitude. The date on the calendar is February 20. The reading on the sundial is 16 o'clock. It is necessary to determine the average “terrestrial” time.

The solution looks like this:

The difference with Greenwich time is calculated: 32°30′ / 15 = 2 hours 9 minutes. Since the longitude is eastern, this means that the clock in the prime meridian, compared to the clock in the given area, will be 2 hours 9 minutes behind.
A correction is made for the equation of time. According to the table of the equation of time for February 20, the indicator is found - it corresponds to +13.9. That is, astronomical time on this day lags behind “earthly” by 13.9 minutes, which corresponds to 13 minutes 54 seconds. This means “earthly” time (but not averaged over the time zone) in this moment will correspond to 16 hours + 13 minutes 54 seconds = 16 hours 13 minutes 54 seconds. Round up to the nearest minute - it turns out to be 16 hours 14 minutes.
Knowing the “earthly” (not average) time in a given area and the difference in hours with the prime meridian, Greenwich time is determined: 16 hours 14 minutes – 2 hours 9 minutes = 14 hours 5 minutes.
Knowing the time zone of the area (+2) in which the measurements are taken, the average “earthly” time in this area is determined: 14 hours 5 minutes + 2 hours = 16 hours 5 minutes.

If the sundial is not planned to be moved to an area with a different longitude, the correction for longitude can be written on the clock itself so as not to recalculate it every time.

It is also important when converting astronomical time to “terrestrial time” not to forget that in some regions clocks are set to summer time. If this is not done, the error may be 1 hour.

Is it possible to buy a sundial?

Today you can see many different models of sundials on sale. Unfortunately, many of them perform a purely decorative function and are not suitable for accurate time measurements. Personally, I was lucky enough to see such a model only once, with the help of which you can actually determine time.

When purchasing a “working” sundial, the first thing you should pay attention to is what type it is. The equatorial type of sundial, as mentioned earlier, is universal, which means that it is likely that they can be installed normally in any area and ensure correct operation.

Such watches should be equipped with a mechanism that allows you to adjust the tilt of the dial, and, if possible, a rotating scale, allowing you to use it in any location.

There are also companies that manufacture custom-made sundials, but their services, as far as I know, are very expensive.

Based on this, it seems to me that it is easier to make a sundial yourself from cardboard or plywood. In this case, a person will not only acquire a really working tool, but will also better understand the principles on which these watches work. And these principles are the fundamental thing of all methods of orientation by the Sun, stars and Moon, so necessary for travelers considering risks emergency situations and studying ways to get out of them.

To summarize all of the above, several points can be noted.

For a person who finds himself in wildlife, sundial and gnomon in particular will allow you to navigate the area. Portable sundials in this regard are more universal tool, since they make it possible to find the approximate location of the cardinal points at any moment of the day, if the time, the coordinates of the area are known, and the Sun is not hidden by clouds. With a stationary sundial everything is even simpler: they make it possible to navigate in cloudy weather and even at night, since, as a rule, they are oriented strictly to the cardinal points.

Sundial functions such as time and date are not so necessary in tourism and emergency survival situations. At least, I have never heard of anyone being seriously injured without knowing the calendar day or local time. If, however, you still need to navigate in time by the Sun, as for me, it is easier to do this if you know the cardinal directions and the direction to the Sun at the moment. Yes, the result will not be very accurate, and in low latitudes this method will be of little help, however, you also won’t have to carry a bulky sundial with you or waste time building one on the ground from scrap materials.

If, nevertheless, there is an urgent need for a sundial, then you should orient it not by a compass, but by the North Star or by the cardinal directions determined using a gnomon. As stated earlier, magnetic poles do not coincide with geographical ones, and the area where the sundial is installed may be in the zone of a magnetic anomaly. All this will not make it possible to correctly set the sundial using a magnetic compass.

Instructions

Equatorial watches got their start due to the fact that the plane of their dial is parallel to the plane of the Earth's equator. To make them, you first need to determine the North. This can be done as follows: having secured the gnomon (vertical pin) on a horizontal plane several hours before solar noon, mark with a dot the location of the shadow of the pin and draw a circle with a compass, the center of which will be in the place where the gnomon is fixed, and the radius will be equal to the length its shadow at the initial moment of observation.

Observing the shadow, you can notice that moving away from the drawn circle, it decreases, but at a certain moment the shadow will begin to grow again and cross the circle again. In the place where the shadow again crossed the circle line, place a second point and connect it to the first. The resulting segment must be divided in half. Passing through the middle of the segment and the center of the circle, the straight line will show us the noon line, which shows exact direction North South.

The resulting structure must be correctly oriented. To achieve this, a number of conditions must be met: - The dial line with numbers 6-18 must be located strictly horizontally;
– The line with numbers 12-24 should coincide with the found north-south direction;
– It is necessary to tilt the plane of the clock dial to the north so that the angle between the horizon plane and the gnomon of the clock is equal to the latitude at which your area is located.

The dial of a horizontal clock is placed strictly horizontally on a stand or ground. The hand of such a clock is a triangle, the angle of which is equal to the latitude of the area. The arrow is pointing north.

The gnomon (in this watch it is made in the form of a triangular hand) is cut out of plastic or plywood. One of the arrow angles is 90° (a right angle), and the other is the latitude of your area. For example, for Moscow the angles of the triangle will be 90° and 55°.

The arrow is installed on a horizontal surface in the place where you plan to place the sundial. Use a compass to find north and orient the gnomon towards it.

To mark the hours on the dial, you need to go up to the timer every hour and make marks, focusing on the shadow of the gnomon.

note

Sundial in middle lane Russia will work only in the summer, because in winter the sun in our latitudes does not rise high enough above the horizon and the gnomon will not provide shade.

A sundial is like the human soul, it only works when it is light.

Instructions

The pillar, which was used as a clock, was called a gnomon. A sundial is a device for determining time by changing the length of the shadow from the gnomon and its movement along the dial. The appearance of these watches is associated with the moment when a person realized the relationship between the length and position of the sun's shadow from certain objects and the position of the sun in the sky. One of the first sundials found in the burial of Nauth (Ireland) dates back to 5000 BC. Obelisks Ancient Egypt and Babylon were used to determine the time of day by the length of the shadow.

The improvement of sundials was carried out greatest philosophers and mathematicians of Ancient Greece - Anaximander, Anaximenes, Eudoxus, Aristarchus. The ancient peoples did not divide the day into 24 equal parts. They divided the daylight hours into 12 hours, from dawn to sunset, so in different time year, the length of the hour was different. In the ancient sundial - scaphis - time was determined by the length of the shadow cast by the gnomon on the surface of a spherical recess marked with complex curves. With the introduction of equal hours of day and night, time began to be determined not by the length of the shadow, but by its direction.

The simplest sundial shows solar time, that is, it does not take into account the division of the Earth into time zones. You can use the sundial only during the day and in the presence of sun. On a sunny day, any pillar casts a shadow. To find out what time it was, people measured the shadow with their steps. In the morning it was longer, at noon it became very short, and in the evening it lengthened again. For many peoples, these obelisks simultaneously served to honor the cult of the Sun God.

In the courtyard of the Museum of Antiquities of the Kerch Historical and Cultural Reserve is exhibited current model sundial. Now anyone can see how the ancient Greeks, who lived on the territory of Kerch hundreds of years ago, measured time. This is a working model, the original is kept on display and museum visitors can see it. The replica clock is installed taking into account all local features and really keeps time on a sunny day.

There are sundials that are horizontal, vertical (if the plane of the dial is vertical and directed from west to east), morning or evening (the plane is vertical, from north to south). Conical, spherical, and cylindrical sundials were also built. In addition to watches made of precious and ordinary metals, stone, wood and paper, people also sought out primitive ways of measuring time by shadow, when the only tool for this was a human hand with five fingers.

The simplest way to measure time using the so-called sundial was that left hand turned the palm up and its pointing upward thumb served as a shadow arrow. Depending on the length of this shadow in comparison with the rest of the fingers of the hand, it was possible to approximately determine the time. This simple method of measuring time was preserved among the rural population very for a long time. As a shadow pointer, a short branch the length of the little finger was sufficient, which was held perpendicularly between the little finger and the ring finger.