Heliograph

File:Heliograph (1)-2.jpg (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 flat{{cite journal |last1=Shackleton |first1=William |title=The Testing of Heliograph Mirrors and the Measurement of Mirrors of Long Focal Length |journal=Transactions of the Optical Society |date=April 1921 |volume=22}} round 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.{{cite book|title=Signal Training|volume=III. Pamphlet No. 2. Heliograph, 5-inch, Mark V. 1922.|year=1922|publisher=His Majesty's Stationery Office|location=London|pages=10–13|url=http://www.royalsignals.org.uk/signals.htm}} 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. 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.[http://www.smecc.org/heliograph_-_signaling_by_the_sun.htm Manual Of Instruction In Army Signaling 1886 Section III- Apparatus And Method Of Using It]. Retrieved on 1 June 2008. Diagrams and instructions for British military heliograph (note British heraldry emblem on cover). The U.S. Army's Signal Corps heliograph used a flat square mirror that did not tilt.{{cite book |last1=Carr |first1=D.J. |title=Manual of Visual Signaling of the US Signal Corps |date=1905 |publisher=Government Printing Office |location=Washington |pages=68 |url=https://books.google.com/books?id=3DtCAQAAMAAJ&pg=PA68&dq=parallel |access-date=16 November 2024}} This type produced flashes by a shutter mounted on a second tripod (Fig 4).W. N. Millar (1920), Canadian Forestry Service. [https://books.google.com/books?id=CI5OAAAAMAAJ Methods of Communication Adapted to Forest Protection] Google Books. Retrieved on 1 June 2008. pp. 160–181 are devoted to the heliograph, with diagrams of the British, American, and Godwin type.

The heliograph had certain 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 military 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 {{cvt|50|ft}} per {{cvt|1|mi}} of range. However, anyone in the beam with the correct knowledge could intercept signals without being detected.Kipling, Rudyard [http://www.kipling.org.uk/poems_codeofmorals.htm A Code of Morals]. The Kipling Society website. Retrieved on 1 June 2008. In the Second Boer War (1899–1902) in South Africa, where both sides used heliographs, tubes were sometimes used to decrease the dispersion of the beam.Major J. D. Harris [http://rapidttp.com/milhist/vol111jh.html WIRE AT WAR – Signals communication in the South African War 1899–1902]. Retrieved on 1 June 2008. Discussion of heliograph use in the Boer War. 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.{{cite web|last=Signals|first=Royal|title=The Heliograph|url=http://royal-signals.org.uk/Datasheets/THE_HELIOGRAPH.php|work=Signalling Handbook (1905)|access-date=15 April 2012}}

The range of a heliograph depends on the opacity of the air and the effective collecting area of the mirrors. Heliograph mirrors ranged from {{cvt|1.5|to|12|in}} 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 {{cvt|20|to|50|mi}} is that the flash of a circular mirror is visible to the naked eye at a distance of {{cvt|10|mi}} for each inch of mirror diameter,{{cite journal |last1=Jacob |first1=W.S. |title=On the Extinction of Light in the Atmosphere |journal=Proceedings of the Royal Society of Edinburgh |date=November 1849 |volume=2 |pages=272–273 |url=https://books.google.com/books?id=OgsFAAAAQAAJ&pg=PA272 |access-date=19 May 2019}} and farther apart seen with a telescope. The world record distance was established by a detachment of U.S. Army signal sergeants by the inter-operation of stations in North America on Mount Ellen, (Utah), and Mount Uncompahgre, (Colorado), {{cvt|183|mi}} apart on 17 September 1894, with Army Signal Corps heliographs carrying mirrors only 8 inches (20 cm) on a side.Coe, Lewis [https://books.google.com/books?id=pzkZPIXm89UC The Telegraph: A History of Morse's Invention and Its Predecessors in the United States]. Google Books. Retrieved on 1 June 2008.

File:Signal mirror Mount Wilson 2014.webm]]

File:Turkish heliograph at Huj2.jpg heliograph military crew at Huj during the First World War, 1917]]

The German professor Carl Friedrich Gauss (1777–1855), of the University of Göttingen developed and used a predecessor of the heliograph (the heliotrope) in 1821.{{cite book|last=Dunnington|first=G. Waldo|title=Carl Friedrich Gauss: Titan of Science|year=2004|publisher=The Mathematical Association of America|location=New York|isbn=0-88385-547-X|pages=122–127|url=https://books.google.com/books?id=_dce9Jaq7iQC&q=heliotrope&pg=PA123}} 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.{{cite journal|title=The Heliotrope|journal=The Manchester Iris|date=7 September 1822|volume=1|issue=32|pages=255–256|url=https://books.google.com/books?id=PDIFAAAAQAAJ&q=heliotrope&pg=PA255|access-date=18 November 2012}} This is the first reliably documented heliographic device,{{cite book|last=Holzmann|first=Gerard|title=The early history of data networks|publisher=IEEE Computer Society Press|year=1995|isbn=0818667826|url=https://archive.org/details/earlyhistoryofda0000holz|url-access=registration|editor=Björn Pehrson|access-date=18 November 2012|page=[https://archive.org/details/earlyhistoryofda0000holz/page/10 10]}} despite much speculation about possible ancient incidents of sun-flash signalling, and the documented existence of other forms of ancient optical telegraphy.

For example, one author in 1919 chose to "hazard the theory"{{cite news|last=Kingman|first=John|title=The Isle of Capri: An Imperial Residence and Probable Wireless Station of Ancient Rome|url=https://books.google.com/books?id=MXJIAAAAYAAJ&q=hazard&pg=PA224|access-date=18 November 2012|newspaper=The National Geographic Magazine|page=224|date=September 1919}} that the Italian mainland signals from the capital of Rome that ancient Roman emperor Tiberius (42 B.C.-A.D.37, reigned A.D.14 to 37), watched for from his imperial retreat on the island of Capri.{{cite book|last=Suetonius|title=The Lives of the First Twelve Caesars|year=1796|publisher=G.G. and J. Robinson, Paternoster-Row|pages=296|url=https://books.google.com/books?id=Ib0_AAAAYAAJ&q=signals&pg=PA296}} 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.

Similarly, the story that a shield was used as a heliograph at the ancient famous Battle of Marathon between the Greeks and Persians in 490 B.C. is also unfortunately a modern myth,{{cite book|last=Krentz|first=Peter|title=The Battle of Marathon|year=2010|publisher=Yale University|isbn=978-0300120851|pages=160|url=https://books.google.com/books?id=ncT8JFn-ed8C&q=modern+myth&pg=PT160}} originating in the 1800s. The ancient historian Herodotus never mentioned any flash.{{cite book|last=Sekunda|first=Nicholas|title=Marathon 490 BC: The First Persian Invasion Of Greece|year=2002|publisher=Osprey Publishing|isbn=1841760005|pages=73|url=https://books.google.com/books?id=pDACy7M7NHoC&q=not+flashed&pg=PA73}} What Herodotus did write was that someone was accused of having arranged to "hold up a shield as a signal".{{cite book|last=Herodotus|title=Herodotus, The Histories, with an English translation by A. D. Godley|year=1920|publisher=Harvard University Press|chapter-url=https://www.perseus.tufts.edu/hopper/text?doc=hdt.+6.115.1|chapter=6.115.1, 6.121.1, 6.123.1,6.124,2}} Suspicion grew in the later 1900s, that the flash theory was implausible.{{cite journal|last=Reynolds|first=P. K. Baillie|title=The Shield Signal at the Battle of Marathon|journal=The Journal of Hellenic Studies|year=1929|volume=49|issue=Part I|pages=100–105|jstor=625005|doi=10.2307/625005|s2cid=161466426 }} The conclusion after testing the theory was "Nobody flashed a shield at the Battle of Marathon".{{cite journal|last=Hodge|first=A. Trevor|title=Reflections on the Shield at Marathon|journal=The Annual of the British School at Athens|year=2001|volume=96|pages=237–259|jstor=30073279|doi=10.1017/s0068245400005281|s2cid=128558448}}

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".Deacon, Richard (1978). The Silent War: a History of Western Naval Intelligence. David & Charles. p. 21. {{ISBN|978-0715375570}}. 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's Persian Gulf Telegraph Department, developed the first widely accepted heliograph about 1869,{{cite journal|last=Mance|first=Henry|title=The Heliograph or Sun Telegraph|journal=United Service Institution of India|date=10 February 1872|volume=1|issue=5|pages=123–130|hdl=2027/mdp.39015035103855?urlappend=%3Bseq=665|url=http://hdl.handle.net/2027/mdp.39015035103855?urlappend=%3Bseq=665|access-date=16 June 2013}}{{cite journal|last=Goode|first=Samuel|title=Mance's Heliograph, or Sun-Telegraph|journal=Journal of the Royal United Service Institution|date=14 June 1875|volume=XIX|issue=LXXXIII|pages=534–548|url=https://books.google.com/books?id=sA5KDfwzI3MC&pg=PA533|access-date=2011-06-21|doi=10.1080/03071847509415772}} while stationed at Karachi (now in modern Pakistan) in the then Bombay Presidency of British India. Mance was familiar with heliotropes by their use earlier for the mapping project of the Great Trigonometrical Survey of India (done 1802–1871). The Mance Heliograph was operated easily by one man, and since it weighed about {{cvt|7|lb}}, the operator could readily carry the device and its supporting tripod. The British Army tested the heliograph in India at a range of {{cvt|35|mi}} with favorable results.{{cite journal|last=Luck|first=George|title=Army Signalling, Heliograph|journal=United Service Institution of India|date=24 May 1872|volume=2|issue=7|pages=101–105|hdl=2027/mdp.39015035103855?urlappend=%3Bseq=801|url=http://hdl.handle.net/2027/mdp.39015035103855?urlappend=%3Bseq=801}} During the Jowaki Afridi expedition sent by the British-Indian government in 1877, the heliograph was first tested in war.{{cite journal|last=Wynne|first=Major A.S.|title=Heliography and Army Signalling Generally|journal=Journal of the Royal United Service Institution|date=15 March 1880|volume=XXIV|issue=CV|pages=235–258|url=https://books.google.com/books?id=nAwmAQAAIAAJ&pg=235|access-date=21 June 2011|doi=10.1080/03071848009417153|url-access=subscription}}R. W. Burns (2004) [https://books.google.com/books?id=Fm6S-CKB630C Communications: An International History of the Formative Years]. Google Books. Retrieved on 2 June 2008. pp. 192-196 discuss the heliograph.

File:AmericanHelio1898Engraving.jpg heliograph instrument, 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 {{cvt|100|mi}} with a lightweight portable instrument.

File:Ruinen aus der Schutztruppen-Zeit Dicker Wilhelm.jpg, where the Germans used to have a Heliographic Station (bird's eye view, 2017)]]

In the United States military, by mid-1878, a younger Colonel Nelson A. Miles had established a line of heliographs connecting far-flung military outposts of Fort Keogh and Fort Custer, in the northern Montana Territory, a distance of {{cvt|140|mi}}.{{cite book |last1=Steinbach |first1=Robert |title=The Lives of Frank and Alice Baldwin |date=1989 |publisher=University of Texas Press |location=Austin |isbn=0-292-74659-8 |page=[https://archive.org/details/lonestarslegacyo00bres/page/136 136] |edition=1 |url=https://archive.org/details/lonestarslegacyo00bres/page/136 }}{{cite journal|last=Reade|first=Lt. Philip|title=About Heliographs|journal=The United Service|date=January 1880|volume=2|pages=91–108|url=https://books.google.com/books?id=nLCgAAAAMAAJ&pg=PA91|access-date=21 June 2011}}{{cite journal |title=The Pacific Slope |journal=Daily Alta California |date=20 September 1884 |volume=37 |issue=12578 |page=5 |url=https://cdnc.ucr.edu/cgi-bin/cdnc?a=d&cl=search&d=DAC18840920.2.58&%2520srpos=1&e=------188-en--20--1--txt-IN-heliograph----1884}} In 1886, United States Army now General Nelson A. Miles (1839–1925), set up a network of 27 heliograph stations in the Arizona and New Mexico territories of the old Southwest during the extended campaign and hunt for the native Apache renegade chief / guerrilla warfare leader Geronimo (1829–1909).{{cite web |last1=Rolak |first1=Bruno |title=General Miles' Mirrors The Heliograph in the Geromino Campaign of 1886 |url=http://huachuca-www.army.mil/pages/history/Rolak.html |website=Fort Huachuca |access-date=19 August 2018 |archive-url=https://web.archive.org/web/20130217145032/http://huachuca-www.army.mil/pages/history/Rolak.html |url-status=dead |archive-date=17 February 2013}} In 1890, now little-known Major W.J. Volkmar of the U.S. Army demonstrated in the Arizona and New Mexico territories, the possibility of performing communication by heliograph over a heliograph network aggregating {{cvt|2,000|mi}} in length.{{cite journal|last1=Greely |first1=Adolphus |title=The Evolution of the Signal Corps |journal=Ainslee's Magazine |date=August 1899 |volume=IV |issue=1 |page=17 |url=https://books.google.com/books?id=q4sXAQAAMAAJ&q=volkmar&pg=PA17 |access-date=31 March 2017 }} The network of communication begun by General Miles in 1886, and continued by unsung and now unfortunately relatively unknown Lieutenant W. A. Glassford, was perfected in 1889 at ranges of {{cvt|85|,|88|,|95|and|125|mi}} over a rugged and broken country, which was the stronghold of the Apache, Commanche and other hostile native Indian tribes.

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.{{citation | publisher = The American Helio-Telegraph and Signal Light Company | year = 1887 | url = https://books.google.com/books?id=Mc90ZgreC8QC | title = An Improved Method in the Art of Signalling for Military and Scientific Purposes | access-date = 1 June 2008}}. In 1888, the U.S. Army Signal Corps reviewed all of these devices, as well as the Finley Helio-Telegraph, and finding none completely suitable, developed its own instrument of the U.S. Army Signal Corps heliograph, a two-tripod, shutter-based machine of {{cvt|13+7/8|lb}} total weight, and ordered 100, for a total cost of $4,205.{{citation | url = https://books.google.com/books?id=88ctAAAAIAAJ | title = Annual Report of the Chief Signal Officer of the Army to the Secretary of War | year = 1889 | access-date = 3 June 2008 | pages= 43–7}}. By 1893, the number of heliographs manufactured for the American Army Signal Corps was 133.{{cite book|title=Report of the Chief Signal Officer|year=1893|publisher=U.S. G.P.O.|pages=671|url=https://books.google.com/books?id=aypHAQAAIAAJ&pg=PA671}}

The heyday of the heliograph was probably the Second Boer War of the 1890s and early 1900s in South Africa, where it was much used by both the British and the native immigrant Boers. 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 signal 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 Army garrisons were besieged in Kimberley, along with the sieges of Ladysmith, and at Mafeking. With land wire telegraph lines cut, the only contact with the outside world was via light-beam communication, helio by day, and signal lamps at night.

File:1940 06 17 Heliograph Helwan Egypt.jpg troops training with a heliograph during the Second World War in North Africa, Egypt, June 1940]]

In 1909, the use of heliography for forestry protection was introduced by the United States Forestry Service in the western States. By 1920, such use was widespread in the US and beginning in the neighboring Dominion of Canada to the north, and the heliograph was regarded as "next to the telephone, the most useful communication device that is at present available for forest-protection services". D.P. Godwin of the U.S. Forestry Service invented a very portable ({{cvt|4.5|lb|disp=sqbr}}) heliograph of the single-tripod, shutter plus mirror type for forestry use.

Immediately prior to the outbreak of World War I (1914–1918), the mounted cavalry regiments of the Russian Imperial Army in the Russian Empire were still being trained in heliograph communications to augment the efficiency of their scouting and reporting roles.{{cite book|first=Vladimir|last=Littauer|page=123|title=Russian Hussar|isbn=978-1-59048-256-8|date=May 2007|publisher=Long Riders' Guild Press }} Following the two Russian Revolutions of 1917, the revolutionary Bolshevik / Communist units of their Red Army during the subsequent Russian Civil War of 1918–1922, made use of a series of heliograph stations to disseminate intelligence efficiently. This continued even a decade later about counter-revolutionary basmachi rebel movements in Central Asia's Turkestan region in 1926.{{citation | url = https://books.google.com/books?id=qKnZtNHJrVAC | title = Central Asia: Aspects of Transition | first = Tom | last = Everett-Heath | access-date = 3 June 2008 | page = 20| isbn = 9780700709564 | year = 2003 | publisher = Psychology Press }}.

During World War II (1939–1945), Union of South Africa and Royal Australian military forces used the heliograph while fighting enemy Nazi German and Fascist Italian forces along the southern coast of the Mediterranean Sea in Libya and western Egypt with fellow defending British military in the desert North African campaign in 1940, 1941 and 1942.

The heliograph remained standard equipment for military signallers in the Royal 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 military force to have the heliograph as an issue item. By the time the mirror instruments were retired, they were seldom used for signalling. However, as recently as the 1980s, heliographs were used by insurgent Afghan mujahedeen forces during the Soviet invasion of Afghanistan in 1978–1979.{{cite book|last=Woods|first=Daniel|title=Military Communications: From Ancient Times to the 21st Century|year=2008|publisher=ABC-CLIO|isbn=978-1851097326|page=208|chapter-url=https://books.google.com/books?id=RBC2nY1rp5MC&q=heliograph&pg=PA211|chapter=Heliograph and Mirrors|editor=Sterling, Christopher}} Signal mirrors are still included in survival kits for emergency signaling to search and rescue aircraft.

Most heliographs of the 19th and 20th centuries were completely manual. 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 done manually. 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 Army military field optical telegraph that could use either lantern or sunlight) were equipped with clockwork heliostats.{{cite book|last1=Ternant|first1=A.-L.|title=Les télégraphes|date=1884|publisher=Hachette|pages=35–65|edition=2nd|url=https://books.google.com/books?id=6wozAQAAMAAJ&q=horlogerie&pg=PA41}} The Mangin apparatus with heliostat was still in service in 1917.{{cite book|last1=Charles-La Vauzelle|first1=Henri|title=Instruction Pratique Sur L'Installation des Communications Optiques dans le Service De la Telegraphie Militaire: Premiere Partie, Communications Optiques de Campagne|date=1912|pages=30–32, 42–43}}{{cite journal|last1=BOUCHETHAL|first1=J.L.|title=LA TÉLÉGRAPHIE OPTIQUE AUX ARMÉES|journal=La Science et la Vie|date=1916|issue=28|pages=337–342|url=http://gallica.bnf.fr/ark:/12148/bpt6k65514029/f351.image.langEN}}{{cite web|title=Ottoman Soldiers Mounting Signal Apparatus, 1917|url=https://www.flickr.com/photos/39206470@N08/14525840798/|website=Flickr|publisher=Ottoman Imperial Archives|access-date=7 September 2015}} 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.{{cite journal|title=The Heliograph in Mauritius|journal=Engineering|date=13 October 1882|volume=34|page=363|url=https://books.google.com/books?id=_5dDAQAAIAAJ&q=mangin+heliograph&pg=PA363}} In 1961, the United States Air Force was working on a space heliograph to signal between satellites{{cite journal|last1=Pursglove |first1=S. David |title=Ancient Heliograph Goes Modern for Space Age |journal=Science and Mechanics |date=1961 |page=70 |url=http://myweb.cableone.net/kd7aoi/spacehg.htm |url-status=dead |archive-url=https://web.archive.org/web/20110525175319/http://myweb.cableone.net/kd7aoi/spacehg.htm |archive-date=25 May 2011 }}

In May 2012, "Solar Beacon" robotic mirrors designed at the University of California at Berkeley were mounted on the twin towers of the Golden Gate Bridge at the entrance to San Francisco Bay, and a web site set up{{cite web|title=Solar Beacon |url=http://solarbeacon.org/? |access-date=30 May 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120530061034/http://solarbeacon.org/ |archive-date=30 May 2012 }} where the public could schedule times for the mirrors to signal with sun-flashes, entering the time and their latitude, longitude and altitude.{{cite web|last1=Boxall|first1=Bettina|title=Golden Gate Bridge is prepared for 75th birthday celebration|url=http://latimesblogs.latimes.com/lanow/2012/05/golden-gate-bridge-prepares-for-special-75th-birthday-celebration.html|website=LA Now|publisher=Los Angeles Times}} The solar beacons were later moved to Sather Tower at the U.C. – Berkeley campus.{{cite news|last1=Tuan|first1=Lydia|title=Solar Beacon atop Campanile allows for safe observation of sunlight|url=http://www.dailycal.org/2013/09/10/solar-beacon-atop-campanile-allows-for-safe-observation-of-sunlight/|work=The Daily Californian|date=10 September 2013}}{{cite web|title=Solar Beacon|url=http://solarbeacon.org/|access-date=7 September 2015}} 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.{{cite web|last1=Vallerga|first1=John|title=Custom Show Setting|url=http://solarbeacon.org/?page_id=156#comment-82|website=Solar Beacon|access-date=28 June 2012}} The designer described the Solar Beacon as a "heliostat", not a "heliograph".

The first digitally controlled heliograph was designed and built in 2015.{{cite web|title=IPA Freshman's science fair project|url=https://islandpacificacademy.org/ipa-freshmans-science-fair-project-1-of-300-best-in-the-nation/|website=Island Pacific Academy|date=3 September 2015 |access-date=6 September 2015}}{{cite web|last1=Welch|first1=Natalie|title=Digital Heliograph|url=https://sites.google.com/site/digitalheliograph/home|access-date=6 September 2015}} It was a semi-finalist in the Broadcom MASTERS competition.{{Cite web|url = https://member.societyforscience.org/document.doc?id=659|title = 2015 Broadcom MASTERS Semifinalists|access-date = 5 September 2015}}

{{Commons category|Heliographs}}

• Heliography, an early photographic process invented by Joseph Nicéphore Niépce around 1822
• Heliotrope (instrument)
• Operation On-Target, a Scouting program
• Signal lamp

{{reflist}}

• Lewis Coe, Great Days of the Heliograph, Crown Point, 1987 {{oclc|16902284}}

{{Commons category|Heliographs}}

• [https://web.archive.org/web/20110525171910/http://myweb.cableone.net/kd7aoi/ Heliography: Communicating with Mirrors] Photographs of British, American and Portuguese heliographs.
• [https://web.archive.org/web/20170222025302/http://www.modulatedlight.org/Modulated_Light_DX/Heliograph.html The Heliograph] A description of the British Mance, Begbie and French LeSeurre heliographs with illustrations (1899)
• [https://www.morsekey.net/eliografo.html Eliografo] Detailed color photographs of a World War 2 British Mance heliograph (Italian).
• [http://trove.nla.gov.au/picture/result?q=heliograph "Heliograph" at the National Library of Australia: Trove]; 100+ historical heliograph photographs at the Australian War Memorial and elsewhere
• [http://home.arcor.de/royal-signals/page24/page26/page26.html Royal Signals Datasheet No. 2. The Heliograph (revised April 2003)] {{Webarchive|url=https://web.archive.org/web/20120905230619/http://home.arcor.de/royal-signals/page24/page26/page26.html |date=5 September 2012 }}
• [https://web.archive.org/web/20121014135758/http://home.arcor.de/royal-signals/page24/page28/page28.html CHAPTER IV THE HELIOGRAPH] (PAGE 48 OF THE 1905 SIGNALLING HANDBOOK)
• [http://www.prc68.com/I/MkVHeliograph.shtml Mance Mark V Heliograph] Detailed photos of a British Mark V Heliograph and kit, links to patents. Clicking on visible photos reveals high resolution photos.
• [http://www.discoverseaz.com/History/Heliograph.html The Heliograph in the Apache Wars]
• [http://samilitaryhistory.org/vol111jh.html Signals communication in the South African War 1899–1902]
• [http://www.douglas-self.com/MUSEUM/COMMS/heliograph/heliograph.htm Heliographs] at the Museum of RetroTechnology

{{Morse code}}

Category:History of telecommunications

Category:Telegraphy

Category:Optical communications