The astrolabe is an amazing “computer” of the ancients. Design, principle of operation and application of the astrolabe Operating principle of the astrolabe

Actually, the title includes the name of a program for creating moving maps of the starry sky, but first, a little history...

The first astronomical instruments appeared long before the advent of modern chronology, and one of the first such instruments was the “astrolabe”. Here's what Wikipedia says about her:

The astrolabe is one of the oldest astronomical instruments, which appeared in Ancient Greece. The ancient Greek astronomer Hipparchus (c. 180-190 - 125 BC) apparently created the prototype of the astrolabe, and Claudius Ptolemy (2nd century) built and described the astrolabon - a goniometric instrument for determining the position of stars.

Over time, the description of the astrolabe first migrated to the Arabs, who made their own improvements to its design, then from the Arabs it came to Europe and now the Europeans, in turn, made some improvements.

At its core, the astrolabe is a two-dimensional model of the celestial sphere - this follows from the name of the device. However, in addition to the astrolabe, a two-dimensional model of the celestial sphere is also a planisphere and a star map. Everything is even much more interesting - it is the astrolabe that is the progenitor of the planisphere. If we look at Russian Wikipedia, we can read the following about the planisphere:

Planisphere (from Latin planum - plane and Greek spháira - ball) is an image of a sphere on a plane in a normal (polar) stereographic projection. Planispheres were used until the 17th century to determine the moments of rising and setting of celestial bodies. Usually they were a coordinate grid applied to metal disk, around the center of which an alidade rotated, facilitating the readings. With the introduction of special tables and nomograms, planispheres fell out of use.

If you believe Wikipedia, then all planispheres have long since “extinct” and can be forgotten about. In fact, the Russian Wikipedia simply does not “say” much about planispheres - to be convinced of this, it is enough to look at the English version of Wikipedia.

There is other confirmation of the fallacy of the statements of their Russian-language wiki, but for this we again need to go back to the past and here I must admit that this will not be possible for everyone.

I know for sure that all the readers of my blog studied at school and some of them had a subject such as “Astronomy” in their graduation class. Even if this subject was not taught at school, but my Reader is an astronomy lover, then you can already guess what will be discussed next - of course, about a moving star chart. This map serves to find out the times of sunrise, culmination and sunset of the celestial bodies. This is its main purpose. As a secondary purpose, it can be used for navigation and as a sidereal clock, but for this you will have to make several efforts. more strength and knowledge than to determine the time of the culmination of the luminary, for example.

This card is a very simple device, consisting of two parts - a fixed card and a movable overhead circle. The map is usually issued with a star pattern for either the northern or southern hemisphere, but the overlay circle is, in theory, very individual - its cutout should only include that part of the sky that is visible at a certain latitude. Accordingly, for different latitudes the overhead circle must be different. This is why moving cards with different overhead circles are mass-produced - when you purchase such a device, pay attention to this. There’s no need to describe it in words, it’s better to look at this device with your own eyes - this is what a Soviet plastic moving star map looks like:


The overhead movable circle on this device is made in the form of a translucent film with a transparent section, the shape of which is made taking into account the latitude of the area. Here is the same map assembled, only a side view:

If you decide to purchase this device at the present time, then a small surprise will await you - you will practically not find it in Russian stores, because... our industry simply does not produce them. But it is produced by the industry of neighboring China at the request of the European Union and the United States. But you still won’t find this device using search engines - they call it differently. Namely: planisphere! Here typical look such a “foreign” moving star map (pay attention to the name!):

However, you can reduce the cost of purchasing this device to a minimum - after all, you can take ready-made patterns for it on the Internet and then do a little crafting. The most difficult thing is to find a pattern for an overlay circle specifically for your latitude and secure it. Luckily I personally dabbled manual assembly this device and I can give a couple of tips on this matter.

So, tip one - to get the correct overlay circle, you can use the Astrolabe program ( Astrolabe in the original and this is a web application) - but for this you need to know geographical coordinates your locality.

Tip two - it’s better to stick a stationary card on a solid base made of thin plywood, thick cardboard or polymethyl methacrylate sheet. Next, we make a hole at the point of the Celestial Pole (it can be drilled with a thin drill). Using the pattern of the overlay circle, first we make a paper cutout, then we take a sheet of polymethyl methacrylate and apply marks on it using this paper cutout outer edge circle, north-south direction, east and west points and oval cutout. Next, carefully cut off all excess - using a jigsaw or needle files, cut out the overhead circle along the external markings. In the resulting part of the device, drill a hole in the center and fasten it to the stationary part - the card - using a bolt, two nuts and three washers (the overhead circle must be movable!).

For the city of Barnaul, I have already generated the corresponding patterns using the Astrolabe and they can be taken in the form of PDF files for subsequent printing:

The astrolabe is one of the oldest astronomical instruments, dating back to Ancient Greece. This ancient instrument was created more than two thousand years ago, when people believed that the Earth was the center of the Universe.

The astrolabe is sometimes called the very first computer. Undoubtedly, this is a device with the deepest mystery and beauty, and we will now try to learn its secrets.

The first astrolabe appeared in Ancient Greece. Vitruvius in his writing “Ten Books on Architecture”, talking about astronomical instrument, called the “spider,” says that it was “invented by the astronomer Eudoxus, while others say Apollonius.” One of the main parts of this instrument was a drum, where the sky with the zodiac circle was drawn.

Stereographic projection was described in the 2nd century AD. e. Claudius Ptolemy in his work “Planispherium”. However, Ptolemy himself called another instrument “astrolabon” - the armillary sphere.

The final type of astrolabe was developed in the 4th century. n. e. Thus, in Alexandria, almost three hundred years after Ptolemy, the mathematician and philosopher Hypatia was condemned by Christian society for satanic rituals, including, among other things, the use of an astrolabe. She was executed in 415 AD. Her student, Theon of Alexandria, left behind copies of notes on the use of the astrolabe.

After the death of Hypatia and after the fall of the Roman Empire, Europe “lost” the astrolabe. Most of the ancient Greek knowledge was lost in Western Europe, whose population regarded ancient Greek (and therefore atheist) technology with great suspicion. However, it was carefully guarded by adherents of Islam; their use of the astrolabe is confirmed by many facts. Without Spain and its Islamic religion, the Renaissance would never have come. Most of the ancient Greek texts found have been translated into Arabic. They were later translated into Latin, and the astrolabe was then reintroduced to the vast majority of Europeans.

Scientists of the Islamic East improved the astrolabe and began to use it not only to determine the time and duration of day and night, but also to carry out some mathematical calculations and for astrological predictions. There are many known works of medieval Islamic authors about various designs and the use of the astrolabe.

These are the books of al-Khorezmi, al-Astrulabi, az-Zarqali, as-Sijizi, al-Fargani, as-Sufi, al-Biruni, Nasir ad-Din at-Tusi and others.

Since the 12th century, astrolabes became known in Western Europe, where they first used Arabic instruments, and later began to make their own according to Arabic models. In the 16th century they began to be made based on their own calculations in order to be used in European latitudes.

The astrolabe reached the peak of its popularity in Europe during the Renaissance, in the 15th-16th centuries; along with the armillary sphere, it was one of the main tools for astronomical education.

Knowledge of astronomy was considered the basis of education, and the ability to use an astrolabe was a matter of prestige and a sign of appropriate education. European masters, like their Arab predecessors, paid great attention decoration, so that astrolabes became fashion items and collectibles at royal courts.

It would be pointless to describe exactly how the astrolabe works - it’s best if you see it with your own eyes.

Shuttle-shaped astrolabe.

As al-Biruni wrote, the design of this astrolabe, invented by al-Sijizi, comes “from the conviction of some people that the ordered movement of the Universe belongs to the Earth, and not to the celestial sphere.” The ecliptic and stars are depicted on its tympanum, and the horizon and almucantarates are depicted on the movable part.

The perfect astrolabe.

In this astrolabe, invented by al-Saghani, the center of projection is not the north pole of the world, but an arbitrary point on the celestial sphere. In this case, the main circles of the sphere are depicted on the tympanum no longer by circles and straight lines, but by circles and conical sections.

Universal astrolabe.

In this astrolabe, invented by al-Zarqali, one of the equinox points is taken as the design center. In this case, the celestial equator and the ecliptic are depicted on the tympanum by straight lines. The tympanum of this astrolabe, unlike the tympanums of ordinary astrolabes, is suitable for any latitude. The functions of the spider of an ordinary astrolabe here are performed by a ruler rotating around the center of the tympanum and called the “moving horizon”.

Spherical astrolabe.

The celestial sphere is represented in this astrolabe as a sphere, and its spider is also spherical.

Observational astrolabe.

This astrolabe is a combination of an armillary sphere and a regular astrolabe, embedded in a ring representing the meridian.

Linear astrolabe.

This astrolabe, invented by Sharaf al-Din al-Tusi, is a rod with several scales, with sighting threads attached to it.

Marine astrolabe.

This device, invented by Portuguese craftsmen at the beginning of the 15th century, is a purely observational device and is not intended for analog calculations.

Marine astrolabe.

Modern encyclopedias say that this device is designed to determine the latitude of a place. In fact, the functions of the astrolabe are much more diverse: it can rightfully be called the computer of a medieval astronomer. Exact number most likely no one can name the functions of the astrolabe, since different types astrolabe could be performed different kinds works Back in the 10th century, the Arab scholar al-Sufi wrote a detailed treatise consisting of 386 chapters, in which he listed 1000 ways to use the astrolabe.

Perhaps he exaggerated slightly, but not by much. After all, with the help of this unique tool it was possible:

Convert the ecliptic coordinates of stars or the Sun into horizontal ones (i.e. determine their altitudes and azimuths);

Using observations of the stars and the Sun through a special viewfinder, determine the latitude of a place, directions to different cities (mainly to calculate the direction to Mecca), determine the time of day, determine sidereal time;

Determine the moments of sunrise and sunset, i.e. the beginning and end of the day, as well as the moments of star rise, and if there were ephemerides, then of the planets; determine the ascending and setting degrees of the ecliptic, i.e. ascendant and descendant, build horoscope houses;

Determine the latitude of an area by measuring the height of the Sun at noon or the heights of the stars at its climax (I’m not sure if this was done often, since using an astrolabe for this purpose is like shooting sparrows with a cannon);

Solve purely earthly problems, such as measuring the depth of a well or the height of an earthly object; and also calculate trigonometric functions(sines, cosines, tangents, cotangents).

Convert between three coordinate systems - equatorial (right ascension and declination), ecliptic (longitude, latitude) and horizontal (azimuth, altitude), and much, much more...

This is how the traditional planispheric astrolabe, usually made of brass, was constructed:

The body most often had a thickness of about 6 mm and a diameter of 15–20 cm (for the largest astrolabes it was up to 50 cm). Although more substantial instruments with a diameter of 30-40 cm were often found, a giant specimen of 85 cm in diameter was known, and, conversely, miniature pocket versions with a diameter of only 8 cm. The fact is that its accuracy directly depended on the size of the astrolabe.

During the heyday of the Arab world, time was measured during the day using a sundial, and at night using a water or sand clock. The astrolabe made it possible to reconcile these watches. To do this, it was necessary to observe the height of the Sun during the day, and at night - one of bright stars, printed on the “spider” of the astrolabe. An interesting device based on the same astrolabe, which can be called a prototype of a mechanical watch, was developed by the famous Arab scientist Al-Biruni. He proposed an astrolabe diagram that automatically showed mutual arrangement Sun and Moon, i.e. lunar phase. The instrument had double body, inside which the gears were fixed. If you rotate the outer disk at a certain speed, you can see the change in the window lunar phases. Later, astrolabes appeared, equipped with gears that simulated the movement of planetary spheres. True, at that time there was no reliable mechanical drive, so the device was fully implemented only in medieval Europe, when the weight and spring drives were invented. And the first mechanical watches, often installed on towers cathedrals in Europe, for a long time were made in the form of astrolabes.

And this is not surprising - after all, complex Arabic astrolabes have turned into real works of art. The star pointers looked not just pins, but spirals and curls in the shape of leaves. The circumference of the instrument was inlaid precious stones and sometimes finished with gold and silver. And all because often a court astrologer would appear with an astrolabe before the menacing eyes of some vizier or shah. An excellent instrument gave weight to the astrologer’s predictions, and not only the fate of the predictor himself depended on this, but also the development of astronomy, more often called then simply the science of the stars.

The incident that allegedly happened to Biruni became a legend. One day, an insidious ruler decided to deal with the unwanted scientist and demanded from him an answer to the question: “Which door - northern or southern - will he leave the hall from?” After performing a series of manipulations with the astrolabe, the resourceful Biruni replied that it would be cut through new door. The answer turned out to be correct. But more often than not, rulers were generous to their court astrologers, allocating money for the construction of observatories and the creation of all kinds of zijs - ephemeris tables. All this led, albeit to a small extent, to progress in astronomy.

The modern descendant of the astrolabe is the planisphere - a movable map of the starry sky, used for educational purposes.

Astronomy is closely related to physics and other sciences of the natural cycle (chemistry, biology, geography). Astronomy uses physical knowledge to explain phenomena and processes occurring in the Universe and to create astronomical instruments.

Invented thousands of years ago goniometric instruments (quadrant, astrolabe)- the first astronomical instruments (Fig. 5,), with the help of which they determined the position of the luminaries in the sky and the time of the onset of celestial phenomena.

Three hundred years ago, the Italian scientist Galileo was first used for astronomical research. telescope- a device that allows you to observe weak objects invisible to the naked eye and increase their apparent size (Fig. 5,).

Figure 5. Ancient astronomical instruments.

Modern astronomy uses more precise instruments for studying celestial bodies, such as the Vega spacecraft and radio telescope (Fig. 6,).

Rice. 6. Modern apparatus for studying celestial bodies.

Of the listed devices and apparatuses, we will dwell in more detail on the astrolabe, which we mentioned in the introduction. Astrolabe is an ancient instrument for determining the position of the Sun and bright stars in different time days throughout the year. The invention of the astrolabe is attributed to Greek astronomers working in the 2nd century BC. Typically, astrolabes were made of copper. Various engravings of the scales made it possible to determine the position of the stars and the Sun at different times of the day throughout the year. Sometimes there were additional scales that provided a variety of information. Most often, astrolabes were made in the form hand tools, so that it can be used to determine the elevation angle of stars (for example, for navigation purposes). Knowing the height and exact time, using the astrolabe it was possible to determine the latitude at which the ship was located.

For two millennia, this scientific instrument remained virtually unchanged. Navigators, starting from 1480 and up to the mid-18th century, used an astrolabe and special tables to determine the latitude of the ship’s location. To reduce measurement error, the diameter of the astrolabe was 13-15 cm, but many English sailors more accurate astrolabes with a diameter of up to 20 cm were used.

By the way, astrolabes of this period (18th century) are also kept in our Tobolsk Historical and Architectural Museum Reserve; we were convinced of this on the virtual excursion “From the History of Inventions” during a physics lesson.

To take measurements in ancient times using an astrolabe, it was necessary to point it at the sun or star. Having recorded the difference in readings between the direction to heavenly body and horizon, and, also knowing the local time, you can use special tables to determine the latitude of a place. This circle was suspended on a ring in a vertical plane, and by means of an alidade equipped with diopters, stars were observed, the height of which was measured on the limb, to which a vernier was subsequently attached. If the latitude was known, then using the same tables it was possible to determine the local time with high accuracy.

Figure 7. Schematic structure of the astrolabe.

The schematic structure of the astrolabe is shown in Figure 7.

The role of the spider here is played by a transparent plate with a map of the starry sky.

The astrolabe is a classic goniometer instrument. Known since the times of the astronomers Hipparchus (II century BC) and Ptolemy (II century AD). The word "astrolabe" comes from Greek words astron (star, in Latin astrum) and lambanw (to take, grasp, in Latin labium - lip). This shows that in ancient times the astrolabe was used to determine angles in the sky. Later, the astrolabe became the main geodetic instrument for measuring angles located in horizontal plane, drawing parallel and perpendicular lines, for taking a terrain plan and others. Until the 18th century it also served to determine latitudes and longitudes.

Astrolabes were used by astronomers and mathematicians, sailors and travelers, architects and builders. Subsequently, the instrument was improved by the Arabs and began to be used to determine time, the length of day and night, and measure horizontal angles on the surface of the Earth, to carry out some mathematical calculations and even for astrological predictions. To create them, sufficiently developed knowledge in the field of mathematics (trigonometry, calculation of spherical celestial coordinates) and astronomy (determining the celestial coordinates of permanent stars, calculating the movement of the Sun and Moon) was required, and it was these sciences that intensively developed in the Arab world. In its heyday Arab Caliphate In the 9th - 11th centuries, astrolabes became widespread. In the form we know, the astrolabe was formed in the East by the 9th - 11th centuries. and then it became most widespread there. In the 11th century devices appear in Spain, and then in other countries of Western Europe. At first, Arabic instruments were used here; Later they began to be made according to Arabic designs in European workshops. If in the East instruments were kept in small cases and were part of a traveling suit ordinary people, then in Europe astrolabes were from the very beginning considered expensive instruments, produced only for the elite. The required precision in drawing lines of complex configurations, the difficulty of manufacturing and the peculiar beauty of these instruments became the reason for their high cost and attractiveness to European sovereigns. Their production began at the royal courts. Having become a fashion item, devices were bought on a par with jewelry. One of the best toolmakers of that time was the Flemish master Gualterus Arsenius (1530-1580). His astrolabes were distinguished by the accuracy of their projections onto the plane of celestial coordinates, scales and elegance of forms, so the Spanish King Philip II ordered their production from him. For many of them, astrolabes were required primarily as astrological instruments, but later, due to their beauty and high cost, they were valued on a par with jewelry. Therefore, one of them, made by G. Arsenius in 1568 and which once belonged to the Austrian commander of the Thirty Years' War (1618-1648) Albrecht Wallenstein, appeared in the 19th century with Grand Duchess Elena Pavlovna. She presented this astrolabe as a gift Public library. Now only 21 astrolabes created by G. Arsenius are known. The only copy in Russia is kept in the M.V. Lomonosov Museum.
The astrolabe consists of several parts made of brass. The main part is a round part with a high side (it was called the “base”, “mother” or “plate”) with a small round hole in the center and a hanging ring for precise orientation of the device relative to the horizon. Three flat round disks are placed in this “plate” - tympanums, also with holes in their center, and the one that corresponds to the latitude of the observation site is placed on top. The fact is that on the surface of each of the tympanums there are projections onto the plane of the lines of the celestial coordinate grid (stereographic projection); celestial meridians, equator, celestial poles, limited by line horizon. The position of the projections of the celestial pole and the celestial coordinate grid will be different for different latitudes of the observation site, therefore each of the tympanums has a projection of the celestial coordinate grid for one of the latitudes - 51°, 51°15’ and 52°. Superimposed on the upper tympanum is a round figured lattice having 45 curved arrows, the ends of which indicate the location of the 45 brightest stars of the Northern Hemisphere in projection onto the plane of the earth's equator. The zodiac circle is also indicated on the lattice. Everything is held together by an axis passing through the central holes of the listed parts. The sighting line is attached to the same axis, which is traditionally called the Arabic term “alidada”. Top part The main disk on both sides of the ring is decorated with the figures of Faun and Faun, who in ancient mythology were associated with the gift of prediction. The astrolabe was used before early XVIII century, until it was supplanted by a more accurate instrument - the sextant (sextant).

Today, things marked by time are in fashion: antiques, various products in and retro. A special chic to the interior based on such decor is given by tools and appliances, which have now lost their relevance, but add a certain flavor and create an atmosphere. These include, for example, a gramophone or a cast iron iron. However, we will not talk about these fairly common units. The focus of the article is the answer to the question of what astrolabes are. These ancient instruments are also now experiencing a rebirth as attributes of styles with a retro or steampunk bent.

Multifunctional tool

The astrolabe, photos of which give a small idea of ​​the use of the object for a person not related to astronomy, is simply beautiful and unusual instrument. However, it has a very specific function. A device was invented for measuring distances from the Earth's surface to stars and planets, which were then used for orientation, determining coordinates, and also astrological predictions. With the help of an ancient astronomical instrument, it was possible to calculate what stars would be there when the Sun would set or rise, and what time it was.

Origin

Already in the second century BC, scientists knew what astrolabes were. The instrument appeared on the territory of Ancient Greece, where it was supplemented and somewhat modified over several centuries. The astrolabe, a photo of which can be found in the article, was brought into this form by Theon of Alexandria in the 4th century. n. e.

Despite its Greek origin, the astrolabe owes a lot to the Arabs. If it weren’t for them, most likely, such an instrument would not have reached us.

Persecution of the Church

The Middle Ages were not the most fertile time for the development of science in Europe. Everything worldly, one way or another trying to explain the world without referring to the concept of God, was declared false and dangerous. After the death of the Roman Empire, the astrolabe was forgotten for centuries in the West. At the same time, a new round of history for the device began in the vastness of Arab countries, where scientists expanded its capabilities.

Update

Eastern masters made their own adjustments to the understanding of what astrolabes are. Now these instruments were used not only for astronomical calculations, terrain orientation and time calculation. Arab astrolabes made it possible to make complex mathematical calculations and predict fate using the stars.

In the vastness of Persia, India and other countries, many books were created containing a description of the structure and use of the instrument for various purposes. All prominent scientists had this device. Both then and later, already in Europe, the science of the stars was revered as the basis of any knowledge, and the astrolabe was a symbol of wisdom. Every astrologer who served as an adviser at the Sultan's court knew how to use the instrument.

Device

The design of the astrolabe consisted of several parts. The base is a circle of brass or copper with a rim around the edge, a hole and a hanging ring in the middle. The latter helped to correctly place the device relative to the horizon line. Along the entire length of the circle there were marks - a scale with divisions, degrees or hours printed on it. The situation of large cities was also often noted.

The so-called tympanum, a disk with a stereographic projection of the starry sky, was placed on the base of the astrolabe. The celestial pole, the north pole and the zenith point with azimuthal circles were marked on it. There were several tympanums for different areas. Each was distinguished by the peculiarities of the position of the zenith point and the horizon line, valid at a given latitude.

A lattice was placed on top of the disk with a projection of the sky, which, due to its structural features, was called a “spider”. It was equipped with pointers to help determine the location. The arrows were often made in the form of elegant leaves or curls, making the whole structure not only convenient in functional terms, but also delivering

Back in Europe

Centuries later, the West again learned what astrolabes are, thanks to the study of the works of Eastern scientists. Europeans began to use Arabic instruments, and then made their own. New examples were also decorated in the manner of their eastern counterparts. Soon, astrolabes became striking specimens in the collections of nobles.

Today this device is a symbol of mysteries: the astrolabe is more often associated in the minds of people with the predictions of astrologers than with the research of astronomers. For example, the device may be associated with a name that many people now know - Astrolabe gave the name to one of the companies that send out dubious predictions of its authorship. But despite such twists of fate, the instrument for most today is part of the history of astronomy, interesting symbol a bygone era and a beautiful attribute.

December 1st, 2011

This ancient instrument was created more than two thousand years ago, when people believed that the Earth was the center of the Universe. The astrolabe is sometimes called the very first computer. Undoubtedly, this is a device with the deepest mystery and beauty

The first astrolabe appeared in Ancient Greece. Vitruvius, in his writing “Ten Books on Architecture,” talking about an astronomical instrument called a “spider,” says that it was “invented by the astronomer Eudoxus, while others say Apollonius.” One of the main parts of this instrument was a drum, where the sky with the zodiac circle was drawn.

Stereographic projection was described in the 2nd century AD. e. Claudius Ptolemy in his work “Planispherium”. However, Ptolemy himself called another instrument “astrolabon” - the armillary sphere. The final type of astrolabe was developed in the 4th century. n. e. Thus, in Alexandria, almost three hundred years after Ptolemy, the mathematician and philosopher Hypatia was condemned by Christian society for satanic rituals, including, among other things, the use of an astrolabe. She was beaten, raped and executed in 415 AD. Her student, Theon of Alexandria, left behind copies of notes on the use of the astrolabe.

After the death of Hypatia, Europe "lost" the astrolabe after the fall of the Roman Empire. Most ancient Greek knowledge was lost in Western Europe, whose population regarded ancient Greek (and therefore atheist) technology with great suspicion. However, it was carefully guarded by adherents of Islam; their use of the astrolabe is confirmed by many facts. Without Spain and its Islamic religion, the Renaissance would never have come. Most of the ancient Greek texts found have been translated into Arabic. They were later translated into Latin, and the astrolabe was then reintroduced to the vast majority of Europeans.

Scientists of the Islamic East improved the astrolabe and began to use it not only to determine the time and duration of day and night, but also to carry out some mathematical calculations and for astrological predictions. There are many works by medieval Islamic authors about various designs and uses of the astrolabe.
These are the books of al-Khorezmi, al-Astrulabi, az-Zarqa, al-Sijizi, al-Fargani, al-Sufi, al-Biruni, Nasir ad-Din at-Tusi and others.

Since the 12th century, astrolabes became known in Western Europe, where they first used Arabic instruments, and later began to make their own according to Arabic models. In the 16th century they began to be made based on their own calculations in order to be used in European latitudes.

The astrolabe reached its peak of popularity in Europe during the Renaissance, in the 15th-16th centuries; along with the armillary sphere, it was one of the main tools for astronomical education.

Knowledge of astronomy was considered the basis of education, and the ability to use an astrolabe was a matter of prestige and a sign of appropriate education. European craftsmen, like their Arab predecessors, paid great attention to artistic design, so that astrolabes became fashion items and collectibles at royal courts.

It would be pointless to describe exactly how the astrolabe works - it is best if you see it with your own eyes.

Shuttle-shaped astrolabe.

As al-Biruni wrote, the design of this astrolabe, invented by al-Sijizi, comes “from the conviction of some people that the ordered movement of the Universe belongs to the Earth, and not to the celestial sphere.” The ecliptic and stars are depicted on its tympanum, and the horizon and almucantarata are depicted on the movable part.

Pictured is an Arabian astrolabe 1090, from the collection of the National Museum of American

The perfect astrolabe. In this astrolabe, invented by al-Saghani, the center of projection is not the north pole of the world, but an arbitrary point on the celestial sphere. In this case, the main circles of the sphere are depicted on the tympanum no longer by circles and straight lines, but by circles and conical sections.

Universal astrolabe. In this astrolabe, invented by al-Zarqali, one of the equinox points is taken as the design center. In this case, the celestial equator and the ecliptic are depicted on the tympanum by straight lines. The tympanum of this astrolabe, unlike the tympanums of ordinary astrolabes, is suitable for any latitude. The functions of the spider of an ordinary astrolabe here are performed by a ruler rotating around the center of the tympanum and called the “moving horizon”.

Spherical astrolabe. The celestial sphere is represented in this astrolabe as a sphere, and its spider is also spherical.

Observational astrolabe. This astrolabe is a combination of an armillary sphere and a regular astrolabe, embedded in a ring representing the meridian.

Linear astrolabe. This astrolabe, invented by Sharaf al-Din al-Tusi, is a rod with several scales, with sighting threads attached to it.

Marine astrolabe. This device, invented by Portuguese craftsmen at the beginning of the 15th century, is a purely observational device and is not intended for analog calculations.

nautical astrolabe.

In the photo, Astrolabe-quadrant, 1325g

Modern encyclopedias say that this device is designed to determine the latitude of a place. In fact, the functions of the astrolabe are much more diverse: it can rightfully be called the computer of a medieval astronomer. Most likely, no one will be able to name the exact number of functions of the astrolabe, since different types of astrolabes could perform different types of work. Back in the 10th century, the Arab scholar al-Sufi wrote a detailed treatise consisting of 386 chapters, in which he listed 1000 ways to use the astrolabe. Perhaps he exaggerated slightly, but not by much. After all, with the help of this unique tool it was possible:

• recalculate the ecliptic coordinates of stars or the Sun into horizontal ones (i.e. determine their altitudes and azimuths);
• using observations of the stars and the Sun through a special viewfinder, determine the latitude of a place, directions to different cities (mainly to calculate the direction to Mecca), determine the time of day, determine sidereal time;
• determine the moments of sunrise and sunset, i.e. the beginning and end of the day, as well as the moments of star rise, and if there were ephemerides, then of the planets; determine the ascending and setting degrees of the ecliptic, i.e. ascendant and descendant, build horoscope houses;

• determine the latitude of an area by measuring the height of the Sun at noon or the heights of the stars at its climax (I’m not sure if this was done often, since using an astrolabe for this purpose is reminiscent of shooting sparrows with a cannon);
• solve purely earthly problems, such as measuring the depth of a well or the height of an earthly object; and also calculate trigonometric functions (sines, cosines, tangents, cotangents).
• make transformations between three coordinate systems - equatorial (right ascension and declination), ecliptic (longitude, latitude) and horizontal (azimuth, altitude), and much, much more...

This is how the traditional planispheric astrolabe, usually made of brass, was constructed.

The body most often had a thickness of about 6 mm and a diameter of 15 - 20 cm (for the largest astrolabes - up to 50 cm). Although more substantial instruments with a diameter of 30-40 cm were often found, a giant specimen of 85 cm in diameter was known, and, conversely, miniature pocket versions with a diameter of only 8 cm. The fact is that its accuracy directly depended on the size of the astrolabe.

The photo shows an example of how to assemble a simple astrolabe.

IN THE PHOTO Astrolabe by Mahmud ibn Shawka al-Baghdadi 1294-1295 diameter - 96 mm. From the collection of the National Maritime Museum, London

During the heyday of the Arab world, time was measured during the day using a sundial, and at night using a water or sand clock. The astrolabe made it possible to reconcile these watches. To do this, it was necessary to observe the height of the Sun during the day, and at night - one of the bright stars marked on the “spider” of the astrolabe. An interesting device based on the same astrolabe, which can be called a prototype of a mechanical watch, was developed by the famous Arab scientist Al-Biruni. He proposed an astrolabe diagram that automatically showed the relative positions of the Sun and Moon, i.e. lunar phase. The tool had a double body, inside of which gears were fixed. If the outer disk was rotated at a certain speed, the change in lunar phases could be observed in the window. Later, astrolabes appeared, equipped with gears that simulated the movement of planetary spheres. True, at that time there was no reliable mechanical drive, so the device was fully realized only in medieval Europe, when weight and spring drives were invented. And the first mechanical clocks, often installed on the towers of cathedrals in Europe, were made in the form of astrolabes for a long time.

And this is not surprising - after all, complex Arabic astrolabes have turned into real works of art. The star pointers looked not just pins, but spirals and curls in the shape of leaves. The circumference of the instrument was inlaid with precious stones and sometimes trimmed with gold and silver. And all because often a court astrologer would appear with an astrolabe before the menacing eyes of some vizier or shah. An excellent instrument gave weight to the astrologer’s predictions, and not only the fate of the predictor himself depended on this, but also the development of astronomy, more often called then simply the science of the stars.

Pictured is a Persian astrolabe 1223

The incident that allegedly happened to Biruni became a legend. One day, an insidious ruler decided to deal with the unwanted scientist and demanded from him an answer to the question: “Which door - northern or southern - will he leave the hall from?” After performing a series of manipulations with the astrolabe, the resourceful Biruni replied that a new door would be cut. The answer turned out to be correct. But more often than not, rulers were generous to their court astrologers, allocating money for the construction of observatories and the creation of all kinds of zijs - ephemeris tables. All this led, albeit to a small extent, to progress in astronomy.

Pictured is a French astrolabe from the late 16th - early 17th centuries.

The modern descendant of the astrolabe is the planisphere - a movable map of the starry sky, used for educational purposes.

This astronomical instrument has made such a long journey through the centuries, without losing its magical charm in our age of computers and powerful telescopes.