Heliograph

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Fig. 1: Signaling with a Mance heliograph, 1910 Heliograph-2.jpg
Fig. 1: Signaling with a Mance heliograph, 1910

A heliograph ( helios (Greek : ἥλιος), meaning "sun", and graphein (γράφειν), meaning "write") is a wireless telegraph that signals by flashes of sunlight (generally using Morse code) reflected by a mirror. The flashes are produced by momentarily pivoting the mirror, or by interrupting the beam with a shutter. [1] The heliograph was a simple but effective instrument for instantaneous optical communication over long distances during the late 19th and early 20th century. [1] Its main uses were military, survey and forest protection work. Heliographs were standard issue in the British and Australian armies until the 1960s, and were used by the Pakistani army as late as 1975. [2]

Helios Ancient Greek personification of the sun

Helios, in Ancient Greek religion and myth, is the god and personification of the Sun, often depicted in art with a radiant crown and driving a horse-drawn chariot through the sky.

Greek language Language spoken in Greece, Cyprus and Southern Albania

Greek is an independent branch of the Indo-European family of languages, native to Greece, Cyprus and other parts of the Eastern Mediterranean and the Black Sea. It has the longest documented history of any living Indo-European language, spanning more than 3000 years of written records. Its writing system has been the Greek alphabet for the major part of its history; other systems, such as Linear B and the Cypriot syllabary, were used previously. The alphabet arose from the Phoenician script and was in turn the basis of the Latin, Cyrillic, Armenian, Coptic, Gothic, and many other writing systems.

Sunlight portion of the electromagnetic radiation given off by the Sun

Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is filtered through Earth's atmosphere, and is obvious as daylight when the Sun is above the horizon. When the direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat. When it is blocked by clouds or reflects off other objects, it is experienced as diffused light. The World Meteorological Organization uses the term "sunshine duration" to mean the cumulative time during which an area receives direct irradiance from the Sun of at least 120 watts per square meter. Other sources indicate an "Average over the entire earth" of "164 Watts per square meter over a 24 hour day".

Contents

Description

Fig. 2: German heliograph made by R. Fuess in Berlin (on display at the Museum of Communication in Frankfurt) Heliograph (1)-2.jpg
Fig. 2: German heliograph made by R. Fuess in Berlin (on display at the Museum of Communication in Frankfurt)

There were many heliograph types. Most heliographs were variants of the British Army Mance Mark V version (Fig.1). It used a mirror with a small unsilvered spot in the centre. The sender aligned the heliograph to the target by looking at the reflected target in the mirror and moving their head until the target was hidden by the unsilvered spot. Keeping their head still, they then adjusted the aiming rod so its cross wires bisected the target. [3] They then turned up the sighting vane, which covered the cross wires with a diagram of a cross, and aligned the mirror with the tangent and elevation screws so the small shadow that was the reflection of the unsilvered spot hole was on the cross target. [3] This indicated that the sunbeam was pointing at the target. The flashes were produced by a keying mechanism that tilted the mirror up a few degrees at the push of a lever at the back of the instrument. If the sun was in front of the sender, its rays were reflected directly from this mirror to the receiving station. If the sun was behind the sender, the sighting rod was replaced by a second mirror, to capture the sunlight from the main mirror and reflect it to the receiving station. [4] [5] The U. S. Signal Corps heliograph mirror did not tilt. This type produced flashes by a shutter mounted on a second tripod (Fig 4). [4]

Shutter (photography) component of a photographic camera

In photography, a shutter is a device that allows light to pass for a determined period, exposing photographic film or a photosensitive digital sensor to light in order to capture a permanent image of a scene. A shutter can also be used to allow pulses of light to pass outwards, as seen in a movie projector or a signal lamp. A shutter of variable speed is used to control exposure time of the film. The shutter is constructed so that it automatically closes after a certain required time interval. The speed of the shutter is controlled by a ring outside the camera, on which various timings are marked.

The heliograph had some great advantages. It allowed long distance communication without a fixed infrastructure, though it could also be linked to make a fixed network extending for hundreds of miles, as in the fort-to-fort network used for the Geronimo campaign. It was very portable, did not require any power source, and was relatively secure since it was invisible to those not near the axis of operation, and the beam was very narrow, spreading only 50 feet per mile of range. However, anyone in the beam with the correct knowledge could intercept signals without being detected. [2] [6] In the Boer War, where both sides used heliographs, tubes were sometimes used to decrease the dispersion of the beam. [2] In some other circumstances, though, a narrow beam made it difficult to stay aligned with a moving target, as when communicating from shore to a moving ship, so the British issued a dispersing lens to broaden the heliograph beam from its natural diameter of 0.5 degrees to 15 degrees. [7]

Geronimo leader of the Bedonkohe Apache

Geronimo was a prominent leader and medicine man from the Bedonkohe band of the Apache tribe. From 1850 to 1886 Geronimo joined with members of three other Chiricahua Apache bands — the Tchihende, the Tsokanende and the Nednhi — to carry out numerous raids, as well as resistance to U.S. and Mexican military campaigns in the northern Mexico states of Chihuahua and Sonora, and in the southwestern American territories of New Mexico and Arizona. Geronimo's raids and related combat actions were a part of the prolonged period of the Apache–United States conflict, which started with American settlement in Apache lands following the end of the war with Mexico in 1848.

Second Boer War War between two Boer Republics and the United Kingdom

The Second Boer War was fought between the British Empire and two Boer states, the South African Republic and the Orange Free State, over the Empire's influence in South Africa. It is also known variously as the Boer War, Anglo-Boer War, or South African War. Initial Boer attacks were successful, and although British reinforcements later reversed these, the war continued for years with Boer guerrilla warfare, until harsh British counter-measures brought the Boers to terms.

The range of a heliograph depends on the opacity of the air and the effective collecting area of the mirrors. Heliograph mirrors ranged from 1.5 inches to 12 inches or more. Stations at higher altitudes benefit from thinner, clearer air, and are required in any event for great ranges, to clear the curvature of the earth. A good approximation for ranges of 20-50 miles is that the flash of a circular mirror is visible to the naked eye for 10 miles for each inch of mirror diameter [8] , and farther with a telescope. The world record distance was established by a detachment of U.S. signal sergeants by the inter-operation of stations on Mount Ellen, Utah, and Mount Uncompahgre, Colorado, 183 miles (295 km) apart on September 17, 1894, with Signal Corps heliographs carrying mirrors only 8 inches square. [9]

Telescope Optical instrument that makes distant objects appear magnified

A telescope is an optical instrument that makes distant objects appear magnified by using an arrangement of lenses or curved mirrors and lenses, or various devices used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. The first known practical telescopes were refracting telescopes invented in the Netherlands at the beginning of the 17th century, by using glass lenses. They were used for both terrestrial applications and astronomy.

Mount Ellen (Utah) mountain in Utah, United States of America

Mount Ellen is a mountain located in Garfield County, Utah. The high point of Mount Ellen's North Summit Ridge is the highest point in the Henry Mountains; it is also the highest point in Garfield County. It can be reached by a short hike from an unpaved road. These mountains were the last to be surveyed by the USGS in the lower 48 states. The mountain can be seen from as far as Mount Peale in the La Sal Mountains of eastern Utah.

Utah U.S. state in the United States

Utah is a state in the western United States. It became the 45th state admitted to the U.S. on January 4, 1896. Utah is the 13th-largest by area, 30th-most-populous, and 11th-least-densely populated of the 50 United States. Utah has a population of more than 3 million according to the Census estimate for July 1, 2016. Urban development is mostly concentrated in two areas: the Wasatch Front in the north-central part of the state, which contains approximately 2.5 million people; and Washington County in Southern Utah, with over 160,000 residents. Utah is bordered by Colorado to the east, Wyoming to the northeast, Idaho to the north, Arizona to the south, and Nevada to the west. It also touches a corner of New Mexico in the southeast.

History

Fig. 3 Ottoman heliograph crew at Huj during World War I, 1917 Turkish heliograph at Huj2.jpg
Fig. 3 Ottoman heliograph crew at Huj during World War I, 1917
Ruins of German Schutztruppe on top of Dikwillem, where the Germans used to have a Heliographic Station (Bird's eye view 2017) Ruinen aus der Schutztruppen-Zeit Dicker Wilhelm.jpg
Ruins of German Schutztruppe on top of Dikwillem, where the Germans used to have a Heliographic Station (Bird's eye view 2017)

The German professor Carl Friedrich Gauss of the University of Göttingen developed and used a predecessor of the heliograph (the heliotrope) in 1821. [1] [10] His device directed a controlled beam of sunlight to a distant station to be used as a marker for geodetic survey work, and was suggested as a means of telegraphic communications. [11] This is the first reliably documented heliographic device, [12] despite much speculation about possible ancient incidents of sun-flash signalling, and the documented existence of other forms of ancient optical telegraphy.

Carl Friedrich Gauss German mathematician and physicist

Johann Carl Friedrich Gauss (; German: Gauß[ˈkaʁl ˈfʁiːdʁɪç ˈɡaʊs]; Latin: Carolus Fridericus Gauss; was a German mathematician and physicist who made significant contributions to many fields in mathematics and sciences. Sometimes referred to as the Princeps mathematicorum and "the greatest mathematician since antiquity", Gauss had an exceptional influence in many fields of mathematics and science, and is ranked among history's most influential mathematicians.

University of Göttingen university in the city of Göttingen, Germany

The University of Göttingen is a public research university in the city of Göttingen, Germany. Founded in 1734 by George II, King of Great Britain and Elector of Hanover, and starting classes in 1737, the Georgia Augusta was conceived to promote the ideals of the Enlightenment. It is the oldest university in the state of Lower Saxony and the largest in student enrollment, which stands at around 31,500.

Heliotrope (instrument) measuring instrument

The heliotrope is an instrument that uses a mirror to reflect sunlight over great distances to mark the positions of participants in a land survey. The heliotrope was invented in 1821 by the German mathematician Carl Friedrich Gauss. The word "heliotrope" is taken from the Greek: helios, meaning "sun", and tropos, meaning "turn". It is a fitting name for an instrument which can be used to "turn" incoming sunlight.

For example, one author in 1919 chose to "hazard the theory" [13] that the mainland signals Roman emperor Tiberius watched for from Capri [14] were mirror flashes, but admitted "there are no references in ancient writings to the use of signaling by mirrors", and that the documented means of ancient long-range visual telecommunications was by beacon fires and beacon smoke, not mirrors.

Tiberius Second Emperor of Ancient Rome

Tiberius was the second Roman emperor, reigning from 14 AD to 37 AD, succeeding Augustus.

Capri island near Naples

Capri is an island located in the Tyrrhenian Sea off the Sorrentine Peninsula, on the south side of the Gulf of Naples in the Campania region of Italy. The main town Capri that is located on the island shares the name. It has been a resort since the time of the Roman Republic.

Similarly, the story that a shield was used as a heliograph at the Battle of Marathon is a modern myth, [15] originating in the 1800s. Herodotus never mentioned any flash. [16] What Herodotus did write was that someone was accused of having arranged to "hold up a shield as a signal". [17] Suspicion grew in the 1900s that the flash theory was implausible. [18] The conclusion after testing the theory was "Nobody flashed a shield at the Battle of Marathon". [19]

In a letter dated 3 June 1778, John Norris, High Sheriff of Buckinghamshire, England, notes: "Did this day heliograph intelligence from Dr [Benjamin] Franklin in Paris to Wycombe". [20] However, there is little evidence that "heliograph" here is other than a misspelling of "holograph". The term "heliograph" for solar telegraphy did not enter the English language until the 1870s—even the word "telegraphy" was not coined until the 1790s.

Henry Christopher Mance (1840–1926), of the British Government Persian Gulf Telegraph Department, developed the first widely accepted heliograph about 1869 [1] [21] [22] while stationed at Karachi, in the Bombay Presidency in British India. Mance was familiar with heliotropes by their use for the Great India Survey. [9] The Mance Heliograph was operated easily by one man, and since it weighed about seven pounds, the operator could readily carry the device and its tripod. The British Army tested the heliograph in India at a range of 35 miles with favorable results. [23] During the Jowaki Afridi expedition sent by the British-Indian government in 1877, the heliograph was first tested in war. [24] [25]

Fig. 4: US Signal Service heliograph, 1898 AmericanHelio1898Engraving.jpg
Fig. 4: US Signal Service heliograph, 1898

The simple and effective instrument that Mance invented was to be an important part of military communications for more than 60 years. The usefulness of heliographs was limited to daytimes with strong sunlight, but they were the most powerful type of visual signalling device known. In pre-radio times heliography was often the only means of communication that could span ranges of as much as 100 miles with a lightweight portable instrument. [9]

In the United States military, by mid-1878, Colonel Nelson A. Miles had established a line of heliographs connecting Fort Keogh and Fort Custer, Montana, a distance of 140 miles. [26] [27] [28] In 1886, General Nelson A. Miles set up a network of 27 heliograph stations in Arizona and New Mexico during the hunt for Geronimo [29] .In 1890, Major W. J. Volkmar of the US Army demonstrated in Arizona and New Mexico the possibility of performing communication by heliograph over a heliograph network aggregating 2,000 miles in length. [30] The network of communication begun by General Miles in 1886, and continued by Lieutenant W. A. Glassford, was perfected in 1889 at ranges of 85, 88, 95, and 125 miles over a rugged and broken country, which was the stronghold of the Apache and other hostile Indian tribes. [9]

By 1887, heliographs in use included not only the British Mance and Begbie heliographs, but also the American Grugan, Garner and Pursell heliographs. The Grugan and Pursell heliographs used shutters, and the others used movable mirrors operated by a finger key. The Mance, Grugan and Pursell heliographs used two tripods, and the others one. The signals could either be momentary flashes, or momentary obscurations. [31] In 1888, the US Signal Service reviewed all of these devices, as well as the Finley Helio-Telegraph, [31] and finding none completely suitable, developed the US Signal Service heliograph, a two-tripod, shutter-based machine of 13 7/8 lb. total weight, and ordered 100 for a total cost of $4,205. [32] In 1893, the number of heliographs manufactured for the US Signal Service was 133. [33]

The heyday of the heliograph was probably the Second Boer War in South Africa, where it was much used by both the British and the Boers. [1] [2] The terrain and climate, as well as the nature of the campaign, made heliography a logical choice. For night communications, the British used some large Aldis lamps, brought inland on railroad cars, and equipped with leaf-type shutters for keying a beam of light into dots and dashes. During the early stages of the war, the British garrisons were besieged in Kimberley, Ladysmith, and Mafeking. With land telegraph lines cut, the only contact with the outside world was via light-beam communication, helio by day, and Aldis lamps at night. [9]

In 1909, the use of heliography for forestry protection was introduced in the United States. By 1920 such use was widespread in the US and beginning in Canada, and the heliograph was regarded as "next to the telephone, the most useful communication device that is at present available for forest-protection services". [4] D.P. Godwin of the US Forestry Service invented a very portable (4.5 lb) heliograph of the single-tripod, shutter plus mirror type for forestry use. [4]

Immediately prior to the outbreak of World War I, the cavalry regiments of the Russian Imperial Army were still being trained in heliograph communications to augment the efficiency of their scouting and reporting roles. [34] The Red Army during the Russian Civil War made use of a series of heliograph stations to disseminate intelligence efficiently about basmachi rebel movements in Turkestan in 1926. [35]

During World War II, South African and Australian forces used the heliograph against German forces in Libya and Egypt in 1941 and 1942. [1]

The heliograph remained standard equipment for military signallers in the Australian and British armies until the 1940s, where it was considered a "low probability of intercept" type of communication. The Canadian Army was the last major army to have the heliograph as an issue item. By the time the mirror instruments were retired, they were seldom used for signalling. [9] However, as recently as the 1980s, heliographs were used by Afghan forces during the Soviet invasion of Afghanistan. [1] Signal mirrors are still included in survival kits for emergency signaling to search and rescue aircraft. [1]

Automated heliographs

Most heliographs of the 19th and 20th century were completely manual. [4] The steps of aligning the heliograph on the target, co-aligning the reflected sunbeam with the heliograph, maintaining the sunbeam alignment as the sun moved, transcribing the message into flashes, modulating the sunbeam into those flashes, detecting the flashes at the receiving end, and transcribing the flashes into the message, were all manual steps. [4] One notable exception – many French heliographs used clockwork heliostats to automatically steer out the sun's motion. By 1884, all active units of the "Mangin apparatus" (a dual-mode French military field optical telegraph that could use either lantern or sunlight) were equipped with clockwork heliostats. [36] The Mangin apparatus with heliostat was still in service in 1917. [37] [38] [39] Proposals to automate both the modulation of the sunbeam (by clockwork) and the detection (by electrical selenium photodetectors, or photographic means) date back to at least 1882. [40] In 1961, the US Air Force was working on a space heliograph to signal between satellites [41]

In May 2012, "Solar Beacon" robotic mirrors designed at UC Berkeley were mounted on the towers of the Golden Gate bridge, and a web site set up [42] where the public could schedule times for the mirrors to signal with sun-flashes, entering the time and their latitude, longitude and altitude. [43] The solar beacons were later moved to Sather Tower at UC Berkeley. [44] [45] By June 2012, the public could specify a "custom show" of up to 32 "on" or "off" periods of 4 seconds each, permitting the transmission of a few characters of Morse Code. [46] The designer described the Solar Beacon as a "heliostat", not a "heliograph". [43]

The first digitally controlled heliograph was designed and built in 2015. [47] [48] It was a semi-finalist in the Broadcom MASTERS competition. [49]

See also

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Further reading