The position of the sun on the map online. How to determine the sunrise and sunset for your locality. Magic dates of the equinox and solstice

"Ras-sve-you! For-ca-you!"(c) Zemfira

"As you're staring at the sun"(c) Dexter Holland

Today the site of the day is the SunCalc service, which displays astronomical information about the Sun on Google maps.

SunCalc Logo

The SunCalc website is not only a fun timekiller for geography fans, but also a great example of what learning materials can be like in the age of the internet. The SunCalc website is another reason to remind the employees of the Ministry of Education that we live in an era of other speeds, other technologies and a different level of demand for information, so a pathetic little book with a boring description of the most boring theses of the subject can no longer claim the proud title of "Textbook" . It's easy to imagine what the textbook of the future could be like if the SunCalc website is just one illustration for one of the lessons. Obviously, there is a lot of work to be done, but you have to start somewhere, and SunCalc is one of such "undertakings".

On the SunCalc website, you can set a place on the map and a circle of the virtual sky will be drawn for it. The orange arc will mark the path that the Sun will take across the sky today (except during the polar night). Light yellow will be painted over the part of the sky in which the Sun has ever been. Colored radii will show the direction of the sun at dawn, at sunset, and right now (if not at night). You can use the real Sun instead of a compass, or you can find the exact position of the Sun in the sky even on the most cloudy day. In parallel, tabular data will be displayed with the time of the onset of the phases of the day, including the three stages of twilight.

Chart for Moscow on the SunCalc website

The most pleasant begins if we compare the indicators for different points on the map. The data from the textbook begins to play with new colors. You can see white nights, polar days, equinoxes, solstices and other phenomena from the life of the Sun on the diagrams. You can feel the lines of the tropics and the equator by touch (on the tropic, the border of the yellow zone will pass through the center of the circle, and on the equator there will be a wide, strictly horizontal yellow stripe). In general, you can stop straining, presenting the data from the textbook in your head, and just see it on the monitor in an extremely visual form.

Those who have not yet read the textbook (or read it, but forgot) will be able to simply see what is happening with the Sun in the world on the SunCalc website, and sooner or later become interested in why it wants to delve into the textbook. It seems to me that this is the easiest way to get people interested in learning, but maybe I'm wrong and boring teachers have better methods.

Here, look, there is so much Sun in Rio, not what we have.

Sometimes, for example, when going on a hike, it is extremely important for us to know the time of sunrise and sunset. I would like to find myself in civilized places before dark. But how do we calculate when to leave and when to return? Easily! Look at the tear-off calendar. There, for each day, it is indicated to the minute when the sun rises and when it sets. Add to this another half an hour or an hour (depending on the distance from the equator and clear/cloudy weather) for dawn and evening twilight, and you get the length of daylight hours.

However, in this advice - to be guided by a tear-off calendar - there is one but. So we will know the time of sunrise and sunset, for example, in Moscow, but by no means in our area. And here we must move from the lyrics to the dry language of numbers. Ready? Then read our article and calculate the daylight hours for your area.

What geographic parameters are involved in the calculation

In relation to our star, the planet Earth rotates at a speed of fifteen degrees per hour. The Sun occupies its highest position in the sky at noon. And in this paragraph, one should take into account the correction for the possible summer time, when the chronometers of many countries willfully (that is, without coordination with the Cosmos) are moved forward an hour. Then the sun is at its zenith at one o'clock in the afternoon. But that's not all.

There is also the concept of "true noon". The earth is divided into time zones. Each of them is quite a vast territory. Therefore, in settlements located to the east or west of the hour meridian (where noon occurs exactly at 12:00), it is observed earlier or later. Thus, it is necessary to establish the longitude at which the settlement of interest to us is located. To determine the sunrise / sunset, we need to know the latitude of the area relative to the equator.

Magic dates of the equinox and solstice

Twice a year, the Earth rotates to our luminary at an angle of 90 degrees. This year it will happen on March 19 and September 22. These days, anywhere in the world, sunrise and sunset will occur at six o'clock (morning and evening, respectively). That's when it's convenient to calculate local time! In the north, dusk and dawn play in the sky for a long time. In tropical latitudes, the sun dives quickly below the horizon. But this is not the main thing. After all, daylight hours can optically become smaller due to simple cloudiness.

Two more dates should be remembered: the winter and summer solstices. For the northern hemisphere, December 21 is the day with the longest night. And on June 21, the sun is in no hurry to leave the sky. On this date, night does not fall on the Arctic Circle, and on December 21 it does not change into daylight. But when does dawn come on the summer and winter solstices in the area of interest to us?

Sunrise and sunset in Moscow

Consider the algorithm for calculating the length of daylight hours and, consequently, the time of dawn and sunset using the example of the capital. On the nineteenth of March in Moscow, however, as elsewhere on the globe, it will be light twelve o'clock. But since the metropolis is located just east of the UTC +3 hour meridian, the sun will rise there not at 6:00, but at 6:38. And it will also come in at 18:38. Daylight continues to increase, reaching its climax at seventeen hours and twenty-five minutes on June 20th. We can easily determine the sunrise and sunset for Moscow on this date. Noon there comes at 12:38. Then it turns out that the sun rises at 3:48 and sets at 21:13. Do you already know the deviation from the hour meridian in your locality? When is true noon there?

Sunrise and sunset at the selected location

The dates of the equinox and solstice can be the starting data for calculations. On March 20, both at the Arctic Circle and at the equator, the sun will rise at 6:00, and sunset will be at 18:00. Here we take into account the deviation from the hour meridian. After the vernal equinox in the Northern Hemisphere, daylight begins to grow, reaching its apogee on June 21. On the Arctic Circle, sunrise and sunset occur at 0:00. Therefore, a day of light lasts twenty-four hours. And at the equator, everything remains the same: dawn at 6:00, sunset at 18:00. The higher the latitude, the longer the daylight hours grow, the earlier the sun rises and the later it sets.

Knowing the geographical coordinates of the point, it is easy to calculate the time of sunrise and sunset. We derive the formula. Find out how many days are between the spring equinox and the summer solstice. Ninety-two days. We also know how many hours a day of light lasts on the summer solstice. Let's say eighteen hours. 18 - 12 = 6. Divide six hours by 92. The result is how many minutes each light day grows. We divide it into two. This is how much earlier the sun rises compared to yesterday.

SunCalc shows on the map for the selected place and date the trajectory of the sun and the phases of illumination during the day (and a couple of pleasant little things).

The idea of it appeared after I needed to find in the Crimea a good place to shoot a frame of the sun going into the sea at sunset (for the clip, they shot it in the end) - it turned out that all the existing means for this were very outdated. I wanted to create my own, making it the best you can imagine, found a good page with a bunch of astronomical formulas, took up the development in free evenings and here is the result.

Capabilities

draws a beautiful vector graph on the map with the position of the sun at dawn, sunset and at the selected time (yellow, orange and red line), the projection of the sun's trajectory (orange arc) and its spread throughout the year (yellow area around it); the closer the point on the graph is to the center of the circle, the higher the sun is above the horizon at that moment
hovering the mouse over the sunset/dawn line shows the corresponding spread of positions
shows lightness (darkness, twilight, daylight) by color on the time slider
you can see the time not only of sunrise and sunset, but also of 3 types of twilight (civil, nautical, astronomical) and complete darkness
shows a link to the weekly weather forecast (cloudiness, precipitation, fog) in the selected location
can determine the location (click on the corresponding field -> Detect my location)
location can also be selected by search, auto-detect, clicking on the map or dragging a marker
Permalinks to a specific place/time and back/forward work in the browser

What can the ego be used for?

First, in purely domestic situations. Until how long do I have to leave the forest, while at least something is visible, if I still have not bought a headlight for my bike? How long can I sunbathe in the evening before the beach is covered by the shadow of the rock on the right? At what time will the sun no longer blind directly into my eyes, when I go out to play football on the playground under the house? What is the level of light in the apartment I'm going to rent during the year? It has already come in handy more than once in such matters.

Secondly, photography lovers! Including me. It is often important to know, for example, when and how long twilight lasts (for night landscapes), in which direction the sun sets or where the sun rises from (in order to choose a good angle), what time to choose for a photo session of an object so that you do not have to photograph against the sun or he did not fall completely into the shadow of a neighboring building, etc.

Third, for general education and the satisfaction of natural curiosity. Why is Australia hotter in winter than in summer? What are white nights really and in what cities and when are they observed? What about the polar day and night? How does the path of the sun change from north to south? How many minutes does dawn take from Moscow to Kyiv? Etc.

Few implementation details

all application code is executed on the browser side
Google Maps API v3 is used for map and search
for vector graphics on the map - Raphaёl library
for location - , Google Gears or Google IP Geolocation
using jQuery and several jQuery UI components (Slider for the time, Datepicker for the date, and Dialog for the welcome box)
for deep linking and ajax history plugin is used here. Thank you!
update: sorry for the hosting problems, the project has temporarily moved to another server - now everything seems to be fine.