This technical textbook is the nineteenth edition of the book by Henry Raper, Lieutenant in the Royal Navy with awards that include F.R.A.S. (Fellow of the Royal Astronomical Society) and F.R.G.S. (Friend of the Royal Geographical Society). The book is dedicated in honour of Rear-Admiral Sir Francis Beaufort K.C.B., Hydrographer to the Admiralty. He was awarded the title K.C.B. (King's Commander) as a Member of the Order of Bath, an order of British Chivalry, The book was first published in 1840 and soon became a resource for navigation students. It includes topics on nautical navigation, astronomy, navigation charts, calculations and mathematical tables, time, tides, ships, longitude, and position at sea. Thomas A. Hull, who revised and expanded this edition, was a Commander in the Royal Navy and had previously been Superintendent of Admiralty Charts used for navigation worldwide by seamen from many walks of life. The publisher, J D Potter of London, was at that time the sole agent for the Admiralty Charts produced by the Royal Navy. Printer Spottswoode and Co.,. was established by William Strachan in 1738. In 1819 his nephews A and R Spottswoode took over the business and bought premises in New-Street Square and Shoe Lane. In 1850 over 200 workers were employed by the firm. and five years later the business became Spottswoode & Co. Andrew Spottswoode invented the Spottswoode Press.This technical book was very popular as a textbook for students of maritime navigation, written and updated by members of the British Royal Navy and relied upon for accurate advice and information. The first edition was published in 1840, this edition was updated, expanded and published in 1891 when ports around the world were filling with travellers, merchants and business people. Title: The Practice of Navigation and Nautical Astronomy Author: Henry Raper, Lieut, R.N., F.R.A.S., F.R.G.S. Nineteenth Edition, revised and enlarged by Commander Thomas A. Hull, R.N., Late Superintendant of Admiralty Charts Dedication: To Rear-Admiral Sir Francis Beaufort K.C.B. Publisher: J D Potter, London, sole agent for the sale of Admiralty Charts Printer: Spottswoode and Co. New-Street Square, London Date: 1891 Small leather hardcover book with gold embossed text and lines on the spine. The Dedication in the book is as follows: - "To Rear-Admiral Sir Francis Beaufort K.C.B. Hydrographer to the Admiralty. Sir, The eminent station which you occupy in the naval scientific world renders it highly gratifying to me to dedicate the following Work to you as a testimony of my regard and esteem; while the general accordance of my views on the subject with those of your more experienced judgement, gives me the greater confidence in laying my labours before the Public. I have the honour to be, Sir, Your obedient servant, HENRY RAPER"flagstaff hill maritime museum, maritime museum, shipwreck coast, flagstaff hill, warrnambool, flagstaff hill maritime village, book, navigation, nautical astronomy, hydrography, nautical charts, nautical navigation, astronomical navigation, admiralty charts, henry raper, thomas a. hull, royal navy, j d potter, royal astronomical society, royal geographical society, calculations, mathematical tables, longitude, latitude, nautical time, location at sea, position at sea, maritime, practical navigation, spottswoode and co., sir francis beaufort, k.c.b., rear-admiral sir francis beaufort, hydrographer to the admiralty, scientific book, naval science

Author W M Smart, M.A., D.SC., F.R.A.S. (William Marshall Smart), (1889-1975) Regius Professor of Astronomy in the University of Glasgow, Instructor-Lieut. in the Royal Navy during World War I. and John Couch Adams Astronomer in the University of Cambridge. In 1943 he was elected as a fellow of the Royal Society of Edinburg. From 1949-1951 he was President of the Royal Astronomical Society and a member of the Royal Institute of Navigation. In 1958 he was awarded the Lorimer Medal of the Astronomical Society of Edinburgh. The publisher firm, Longmans, Green & Co, was originally founded in 1724 in London by Thomas Longman under the name Longman. In August of that year, he bought the two shops and goods of William Taylor and set up his publishing house there at 39 Paternoster Row. The shops were called Black Swan and Ship, and it is said that the 'ship' sign was the inspiration for Longman's Logo. After many changes of name and management, the firm was incorporated in 1926 as Longmans, Green & Co. Pty Ltd. The firm was acquired by Pearson in 1968 and was known as Pearson Longman or Pearson PLC. The book was sold by Collins Book Depot which was founded by Frederick Henry (Harry) Slamen in 1922. In 1929 the form became a Proprietary Limited Company with an additional two stores, at 95 Elizabeth and 361 Swanston Streets, Melbourne. Collins Booksellers is still owned by the Stamen family. It is the largest Australian-owned bookselling chain.The book is significant due to its connection with navigation at sea. Its author W M Smart was a learned astronomer and an Instructor-Lieutenant for the Royal Navy during World War I. His achievements were recognised in 1958 when he was awarded the Lorimer Medal of the Astronomical Society of Edinburgh.A Handbook of Sea Navigation: The Theory & Practice of Astronomical Navigation at Sea, with diagrams and charts Author: W M Smart, M.A., D.SC., F.R.A.S. (William Marshall Smart) Publisher: Longmans, Green and Co Printer: Collins Book Depot Date: 1943 Textured green hardcover book. Inscriptions on the Fly page.Pencil: "12/6" [12 shillings 6 pence] Sticker: "G.F. Byrne / Faunce Crescent / O'Connor, A.C.T. / Australia 2001" Stamp: "COLLINS BOOK DEPOT PTY. LTD. / Technical Book Department / 361 Swanston St., Melb. G - - -"flagstaff hill, flagstaff hill maritime museum and village, warrnambool, maritime museum, maritime village, great ocean road, shipwreck coast, longmans green and co., thomas longman, paternoster row london, w m smart, william marshall smart, astronomer, navigator, professor of astronomy, 1943, g.f. byrne, collins book depot, technical book department, 361 swanston st., melbourne, frederick henry (harry) slamen, 361 swanston street melbourne, a handbook of sea navigation, maritime handbook, navigation instructiono, sea navigation

329 pages, illustrated, navy blue linen cover and red paper dust jacket.non-fictionThis volume of the Admiralty Manual of Navigation describes off-shore navigation - the safe conduct of a ship across the open sea where, in general, hearings of objects on land cannot be obtained except by means of radio waves (i.e. using radio fixing aids). The first chapters are mainly concerned with distances, courses, tracks and charts; then various methods of obtaining position lines and positions from astronomical observations are explained, including a rapid. method in the last chapter. The volume also contains an outline of meteorrology and weather forecasting.howard timbury, first fleet fellowship victoria, interest group, navigation, education

544 pages, illustrated, navy blue linen cover and red paper dust jacket.non-fictionThis revised edition follows the previous editions in giving a practical guide to navigation and pilotage which, although written primarily for naval officers, will be suitable for all students of navigation. Astronomical navigation and meteorology can be read in Volume II of this manual. The quality of detailed thoroughness that has always distinguished this book is retained, and it has been brought up to date, particularly in the chapters on radio aids to navigation and navigational instruments.howard timbury, first fleet fellowship victoria, interest group, navigation, education

An octant is an astronomical instrument used in measuring the angles of heavenly bodies such as the sun, moon and stars at sea in relation to the horizon. This measurement could then be used to calculate the altitude of the body measured, and then the latitude at sea could also be calculated. The angle of the arms of an octant is 45 degrees, or 1/8 of a circle, which gives the instrument its name. Two men independently developed the octant around 1730: John Hadley (1682–1744), an English mathematician, and Thomas Godfrey (1704–1749), a glazier in Philadelphia. While both have a legitimate and equal claim to the invention, Hadley generally gets the greater share of the credit. This reflects the central role that London and the Royal Society played in the history of scientific instruments in the eighteenth and nineteenth century's. There were also two others who are attributed to having created octanes during this period, Caleb Smith, an English insurance broker with a strong interest in astronomy (in 1734), and Jean-Paul Fouchy, a mathematics professor and astronomer in France (in 1732) In 1767 the first edition of the Nautical Almanac tabulated lunar distances, enabling navigators to find the current time from the angle between the sun and the moon. This angle is sometimes larger than 90°, and thus not possible to measure with an octant. For that reason, Admiral John Campbell, who conducted shipboard experiments with the lunar distance method, suggested a larger instrument and the sextant was developed. From that time onward, the sextant was the instrument that experienced significant development and improvements and was the instrument of choice for naval navigators. The octant continued to be produced well into the 19th century, though it was generally a less accurate and less expensive instrument. The lower price of the octant, including versions without a telescope, made it a practical instrument for ships in the merchant and fishing fleets. One common practice among navigators up to the late nineteenth century was to use both a sextant and an octant. The sextant was used with great care and only for lunar sightings while the octant was used for routine meridional altitude measurements of the sun every day. This protected the very accurate and pricier sextant while using the more affordable octant for general use where it performs well. The invention of the octant was a significant step in providing accuracy of a sailors latitude position at sea and his vessels distance from land when taking sightings of land-based landmarks.Octant with metal handle, three different colored shades are attached, in wooden wedge-shaped box lined with green felt. Key is attached. Two telescope eyepieces are in box. Some parts are missing. Oval ink stamp inside lid of box, scale is graduated to 45 degrees. Ink stamp inside lid of box "SHIPLOVERS SOCIETY OF VICTORIA. LIBRARY"instrument, flagstaff hill, warrnambool, shipwrecked coast, flagstaff hill maritime museum, maritime museum, shipwreck coast, flagstaff hill maritime village, great ocean road, octant, navigation, nautical instrument, navigation instrument, john hadley, sextant, astronomical instrument

In 1941, the scientific instrument manufacturing firms of  Henry Hughes & Son Ltd, London, England, and  Kelvin Bottomley & Baird Ltd, Glasgow, Scotland, came together to form Kelvin & Hughes Ltd. Kelvin Company History: The origins of the company lie in the highly successful and strictly informal relationship between William Thomson (1824-1907), Professor of Natural Philosophy at Glasgow University from 1846-1899 and James White, a Glasgow optical maker. James White (1824-1884) founded the firm of James White, an optical instrument maker in Glasgow in 1850 and was involved in supplying and mending apparatus for Thomson university laboratory and working with him on experimental constructions. White was declared bankrupt in August 1861 and released several months later. In 1870, White was largely responsible for equipping William Thomson laboratory in the new University premises at Gilmore hill. From 1876, he was producing accurate compasses for metal ships to Thomson design during this period and this became an important part of his business in the last years of his life. He was also involved in the production of sophisticated-sounding machinery that Thomson had designed to address problems encountered laying cables at sea, helping to make possible the first transatlantic cable connection. At the same time, he continued to make a whole range of more conventional instruments such as telescopes, microscopes and surveying equipment. White's association with Thomson continued until he died. After his death, his business continued under the same name, being administered by Matthew Edwards (until 1891 when he left to set up his own company. Thomson who became Sir William Thomson and then Baron Kelvin of Largs in 1892, continued to maintain his interest in the business after James White's death. In 1884 raising most of the capital needed to construct and equip new workshops in Cambridge Street, Glasgow. At these premises, the company continued to make the compass Thomson had designed during the 1870s and to supply it in some quantity, especially to the Admiralty. At the same time, the firm became increasingly involved in the design, production and sale of electrical apparatus. In 1899, Lord Kelvin resigned from his University chair and became, in 1900, a director in the newly formed limited liability company Kelvin & James White Ltd which had acquired the business of James White. At the same time Kelvin's nephew, James Thomson Bottomley (1845-1926), joined the firm. In 1904, a London branch office was opened which by 1915 had become known as Kelvin, White & Hutton Ltd. Kelvin & James White Ltd underwent a further change of name in 1913, becoming Kelvin Bottomley & Baird Ltd. Hughes Company History: Henry Hughes & Sons were founded in 1838 in London as a maker of chronographic and scientific instruments. The firm was incorporated as “Henry Hughes & Sons Ltd” in 1903. In 1923, the company produced its first recording echo sounder and in 1935 a controlling interest in the company was acquired by S Smith & Son Ltd resulting in the development and production of marine and aircraft instruments. Following the London office's destruction in the Blitz of 1941, a collaboration was entered into with Kelvin, Bottomley & Baird Ltd resulting in the establishing “Marine Instruments Ltd”. Following the formal amalgamation of Kelvin, Bottomley & Baird Ltd and Henry Hughes & Sons Ltd in 1947 to form Kelvin & Hughes Ltd. Marine Instruments Ltd then acted as regional agents in the UK for Kelvin & Hughes Ltd who were essentially now a part of Smith's Industries Ltd founded in 1944 and the successors of S. Smith & Son Ltd. Kelvin & Hughes Ltd went on to develop various marine radar and echo sounders supplying the Ministry of Transport, and later the Ministry of Defence. The firm was liquidated in 1966 but the name was continued as Kelvin Hughes, a division of the Smiths Group. In 2002, Kelvin Hughes continues to produce and develop marine instruments for commercial and military. G. Falconer Company History: G Falconer (Hong Kong Ltd) appear to have had a retail presence in Hong Kong since 1885, according to the company website, and currently have a shop in the Peninsula Hotel. G Falconer was the Hong Kong selling agent for several British companies. Ross Ltd of 111 New Bond St London was one and the other was Kelvins Nautical Instruments. Falconers were primarily watchmakers, jewellers and diamond merchants.They were also agents for Admiralty Charts, Ross binoculars and telescopes, and sold English Silverware and High Class English Jewellery. In 1928 the company was operating from the Union Building opposite the Hong Kong general post office. It is unclear if the item is an original Sextant made by Kelvin prior to his amalgamation with Henry Hughes & Sons in 1941 as Kelvin appears to have only made compasses up to this date. If the Sextant can be established that it was made by Kelvin then it is very significant and a rare item made for and distributed through their Hong Kong selling agents G Falconer Ltd. There are many Sextants advertised for sale stating "Kelvin & Hughes 1917 model sextant". These can be regarded as replicas as the company was not formed until 1941 and production of marine instruments was not fully under way until after the war in 1947. Further investigation needs to be undertaken to accurately determine the provenance of this item. As the writer currently has the impression that the subject object was possibly made by Kelvin and Hughes in the mid to late 20th century or is a replica made by an unknown maker in the late 1970s. Purchased as an exhibition of marine navigational instruments for the Flagstaff Hill museum. The Sextant is a brass apparatus with filters and telescope lens, and comes with a wooden felt lined storage box. It is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation.G Falconer and Co. Hong Kong (retailers of nautical equipmentflagstaff hill, warrnambool, shipwrecked-coast, flagstaff-hill, flagstaff-hill-maritime-museum, maritime-museum, shipwreck-coast, flagstaff-hill-maritime-village, sextant, kelvin & hughes ltd, hong kong, navigational instrument, g falconer, mariner's quadrants

An Octant is a doubly reflecting navigation instrument used primarily by sailors to measure the angular distance between two visible objects and was a forerunner of the sextant. The name comes from the Latin octo, or "one-eighth of a circle," for the Octan'ts arc which spans 45°, or one-eighth of a circle. The primary use of an Octant is to measure the angle between an astronomical object and the horizon for celestial navigation. The estimation of this angle, is known as sighting or shooting the object, or taking a sight. The angle, and the time when it was measured, can be used to calculate a position line on a nautical chart (latitude), for example, sighting the Sun at noon or Polaris at night (in the Northern Hemisphere) gives an angle by which the latitude can then be estimated. Sighting the height of a landmark on land can also give a measure of distance. This fine octant once belonged to Captain Farquhar Chisholm and was donated by his granddaughter, Margaret Ruth Greer (nee Chisholm, born 1914). The label inside the Octant's box reads “Thomas L. Ainsley, Instrument Maker … etc”. Farquhar Chisholm was born in 1832 in Inverness, Scotland. He regularly sailed on perilous voyages between Quebec, Canada and the Baltic ports of Europe. In 1854 he migrated to Australia during the Gold Rush, to a place called Fiery Creek (near Beaufort Victoria) where he was fairly successful in his quest for gold. In the years of the Great Gold Rush, it was said that there were over 40,000 diggers in the goldfields of the Beaufort area! In 1857 having made sufficient money, he hired another crew and returned to Clachnacuddin, Inverness shire, Scotland and in that same year, he studied and obtained his Master Mariner Certificate (which would have included the use of an octant for navigation). He was appointed to Mr George (or James) Walker, as commander of his sailing ship, the 3-masted ELIZABETH, built 1859 and known as “The Walker barque”. In 1870 he married, then in 1887 returned to Australia with his wife and children (Kenneth Chisholm (1871), Mary Bremner Chisholm (1873), Margaret Hood Chisholm (1874), Farquhar Chisholm (1878)). They arrived in Port Melbourne, Victoria and sadly, only six weeks after landing, his wife Caroline passed away (in Geelong,1888). In 1900 Capt. Chisholm lived in Camperdown (Victoria) and not long after this his daughter Margaret died of consumption. In his later years, he went to live in the manse of St. Paul’s Presbyterian Church, Wangaratta, with his son, Rev. Farquhar Chisholm. He died there on Sat, 23rd March 1912, 80 years old. He was known as “… quiet, unobtrusive and competent, respected by all with whom he came in contact”. Some other members of Captain Chisholm’s family are; his older son Kenneth Chisholm, who was a contractor in Camperdown; a nephew Donald Macintosh (of 23 Douglas Row, Inverness); a grandson Brian Jones (son of Caroline Belle-Jones nee Chisholm, who lived in Camperdown in the earlier part of her life).The octant, the forerunner of the sextant, was a significant step in providing accuracy of a sailors latitude position at sea & his vessels distance from land when taking sightings of land-based landmarks.Octant, once belonging to Captain Farquhar Chisholm. Wedge shape (the size of an eighth of a circle), made of wood, glass and metal. Used in the 1880s. Maker’s name across centre “L. SIMON - - - SHIELDS”. Three (3) light filtering, coloured glass shades. Two (2) eyepieces. Scale attached for measuring angles. Label inside the fitted, wedge-shaped case "Thomas L. Ainsley, Optician"Label inside case "Thomas L. Ainsley, Optician" Maker’s name across centre “L. SIMON - - - SHIELDS”.flagstaff hill, warrnambool, shipwrecked-coast, flagstaff-hill, flagstaff-hill-maritime-museum, maritime-museum, shipwreck-coast, flagstaff-hill-maritime-village, maritime navigation, navigation instrument, migration, captain chisholm, farquhar chisholm, sailing ship, the elizabeths, thomas l. ainsley, l. simons, shields england, octant, john hadley, chisholm

A sextant is an astronomical instrument used to determine latitude and longitude at sea by measuring angular distances, especially the altitudes of the sun, moon, and stars. It is a doubly reflecting navigation instrument and used mainly by sailors to measure the angular distance between two visible objects. The name comes from the Latin sextans, or “sixth part of a unit,” because the sextant’s arc can be 60° or 120° of a circle depending on the model used. The primary use was to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation. The estimation of this angle is known as sighting or shooting the object, or taking a sight. This angle and the time when it was measured is used in order to determine Greenwich Mean Time and hence longitude. Sighting the height of a landmark on land can also give a measure of distance from that object. History: The development of the sextant was as an improvement over the octant, an instrument designed to measure one's latitude. The octant was first implemented around 1731-present but can only measure angles up to 45°. As larger angles were needed to allow the measurement of lunar objects - moon, stars and the sun - at higher angles, the octant was superseded by the sextant. The sextant is a similar instrument but better made and allows larger angles from 60° to 120°. This improvement allows distances to be accurately calculated thereby giving longitude when used with a chronometer. The sextant was derived from the octant in 1757, eventually making all previous instruments used for navigational positioning obsolete. The sextant had been attributed to by John Hadley (1682–1744) and Thomas Godfrey (1704–1749), but reference to the sextant was also found later in the unpublished writings of Isaac Newton (1643–1727). Earlier links can be found to Bartholomew Gosnold (1571–1607) indicating that the use of a sextant for nautical navigation predates Hadley's implementation. In 1922, the sextant was modified for aeronautical navigation by Portuguese navigator and naval officer Gago Coutinho. It should be noted that the octant and quadrant are in the same family as they were, and all are, regarded as sextants. The sextant is representative of it's type and although not fully complete it demonstrates how 18th,19th and 20th century mariners determined their latitude and longitudinal to determine their position on a chart, allowing them to navigate there way across the world's oceans. It also demonstrates the skill and workmanship of the early instrument makers that operated scientific instrument businesses from London and other areas of England to provide most of the navigational instrumentation used by commercial and military navies of the time.Sextant with square, fitted box of polished wood, "Hezzanith" brand. Box contains many parts for the sextants use. On certificate "Heath & Co, London. Sextant Number Y 822". Catch on lid "DEFIANT LEVER" and "PATENT NUMBER 187.10". Maker's certificate is attached to the inside of the box.flagstaff hill, warrnambool, shipwrecked-coast, flagstaff-hill, flagstaff-hill-maritime-museum, maritime-museum, shipwreck-coast, flagstaff-hill-maritime-village, sextant box, sextant, hezzanith, heath & co, navigational instrument, george wilson heath, astronomical instrument, instrument manufacturers, scientific instrument, navigation, celestial navigation, octant, quadrant, lunar navigation

This sextant is very similar to a 1915 Sextant design. A sextant is an astronomical instrument used in measuring angular distances especially the altitudes of sun, moon and starts at sea determining latitude and longitude.This sextant is an example of a 19th-century marine instrument used for finding location at sea. It was made by London scientific instrument maker Troughton and Simms, which originated in 1826 and continued until 1922.Sextant and its fitted square wooden box. The handle of the sextant is carved with a cross-hatched pattern. Made by Troughton and Simms, London.flagstaff hill, warrnambool, shipwrecked-coast, flagstaff-hill, flagstaff-hill-maritime-museum, maritime-museum, shipwreck-coast, flagstaff-hill-maritime-village, sextant, navigational instrument, marine navigation, marine equipment, instrument, navigation, troughton and simms, london, scientific instrument

This Dollond Day or Nigh telescope was designed to be used in any light conditions, as its name implies. Telescopes are optical instruments designed to make objects appear to be larger or closer. The discovery of the first telescope in 1608 can be attributed to Hans Lippershey of the Netherlands when he discovers that holding two lenses up some distance apart bring objects closer. He applies for a patent on his invention and this becomes the first documented creation of a telescope. Then in 1668, Newton produces the first successful reflecting telescope using a two-inch diameter concave spherical mirror. This opened the door to magnifying objects millions of times far beyond what could ever be obtained with a lens. It wasn’t until 1729 that Chester Moor Hall develops an achromatic lens (two pieces of glass with different indices of light refraction combined produce a lens that can focus colours to almost an exact point resulting in much sharper images but still with some distortion around the edges of the image. Then in 1729 Scottish instrument maker James Short invents the first parabolic and elliptic, distortion-less mirror ideal for reflecting telescopes. We now come to John Dollond who improves upon the achromatic objective lens by placing a concave flint glass lens between two convex crown glass lenses. This had the effect of improving the image considerably. Makers Information: John Dollond (1707-1761) London England he was a maker of optical and astronomical instruments who developed an achromatic (non-colour distorting) refracting telescope and practical heliometer. A telescope that used a divided lens to measure the Sun’s diameter and the angles between celestial bodies. The son of a Huguenot refugees Dollond learned the family trade of silk weaving. He became proficient in optics and astronomy and in 1752 his eldest son, Peter joined his father in an optical business, in 1753 he introduced the heliometer. In the same year, he also took out a patent on his new lenses. He was elected a fellow of the Royal Society in May 1761 but died suddenly in November and his share in the patent passed to his son Peter. In subsequent squabbles between Peter and the many London opticians who challenged his patent, Peter’s consistent position was that, whatever precedents there may have been to his achromatic lenses, his father had independently reached his practical technique on the basis of his theoretical command of Newtonian optics. As a result of maintaining his fathers patent, Dollond s became the leading manufacturer of optical instruments. For a time in the eighteenth and nineteenth century the word 'Dollond' was almost a generic term for telescope rather like 'Hoover; is to vacuum cleaner. Genuine Dollond telescopes were considered to be amongst the best. Peter Dollond (1731-1820) was the business brain behind the company which he founded in Vine Street, Spitalfields in 1750 and in 1752 moved the business to the Strand London. The Dollonds seem to have made both types of telescopes (reflecting and refracting), possessing the technology to produce significant numbers of lenses free of chromatic aberration for refracting telescopes. A Dollond telescope sailed with Captain Cook in 1769 on his voyage to observe the Transit of Venus. Thomas Jefferson and Admiral Lord Nelson were also customers of the Dollonds. Dollond & Co merged with Aitchison & Co in 1927 to form Dollond & Aitchison, the well-known high street chain of opticians, now fully part of Boots Opticians. They no longer manufacture but are exclusively a retail operation.    John Dollond's experiments in optics and how different combinations of lenses refract light and colour gave a better understanding of the divergent properties of lenses. That went on to inform and pave the way for the improvement of our understanding of optics that is represented today. Dollond was referred to in his time as the "Father of practical optics" as a leader in his field he received many prestigious awards. The telescope in the collection is a good example of one of Dollond's early library telescopes. Its connection with one of England's 18th century pioneers in optical development makes it a significant and an important item to have within the collection.Telescope: Dollond's Telescope, Day or Night model navigational instrument. Telescope is mounted on wooden tripod stand that has folding legs. Brass telescope with leather sheath over barrel, adjustable angle fitting with brass wing nuts that join the legs to the top frame, which is then joined to the telescope pole by an adjustable screw fitting. Manufactured by Dollond, London. Inscription reads "Dollond London, Day or Night" and "DOLLOND LONDON"flagstaff hill, warrnambool, shipwrecked-coast, flagstaff-hill, flagstaff-hill-maritime-museum, maritime-museum, shipwreck-coast, flagstaff-hill-maritime-village, telescope, dollond, dollond london, day & night telescope, floor-standing telescope, optical instrument, john dollond, peter dollond, achromatic telescope, heliometer, light refraction, instrument maker, lens, transit of venus, astronomical telescope, concave lens, library telescope, dollond telescope, day or night, day or night telexcope, scientific instrument, navigation, navigational instrument, astronomy

An Octant is a doubly reflecting navigation instrument used primarily by sailors to measure the angular distance between two visible objects and was a forerunner of the sextant. The name comes from the Latin octo, or “one-eighth of a circle,” for the Octant’s arc which spans 45°, or one-eighth of a circle. The primary use of an Octant is to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation. The estimation of this angle is known as sighting or shooting the object, or taking a sight. The angle, and the time when it was measured, can be used to calculate a position line on a nautical chart (latitude), for example, sighting the Sun at noon or Polaris at night (in the Northern Hemisphere) gives an angle by which the latitude can then be estimated. Sighting the height of a landmark on land can also give a measure of distance. History: The principle of the Octant as an instrument to measure ones latitude was first implemented around 1742-present but was superseded by the improvement of the octant to a sextant, a very similar instrument, better made and able to measure bigger angles 120°, allowing the measurement of Luna distances to give longitude when used with an accurate chronometer. The sextant started to appear around 1730 and had been attributed to by John Hadley (1682–1744) and Thomas Godfrey (1704–1749), but reference to the sextant was also found later in the unpublished writings of Isaac Newton (1643–1727). Earlier links can be found to Bartholomew Gosnold (1571–1607) indicating that the use of a Sextant for nautical navigation predates Hadley's implementation. In 1922, the sextant was modified for aeronautical navigation by Portuguese navigator and naval officer Gago Coutinho. Henry Hemsley was a lesser-known instrument maker and optician working in London in the late 17th and early 18th century. However, it should be noted that there were two Henry Hemsley opticians and instrument makers around this period. (Henry Hemsley 1, 1786-89, who had premises at 85 Fleet St London and Henry Hemsley 2, 1828-56), whose workshop was at 135-138 Radcliff Highway London. Therefore, based on the inscribed workshop address Henry Hemsley 2 is responsible for making this example.The octant is representative of its type and although not fully complete it demonstrates how 18th and 19th-century mariners determined their latitude on a chart to navigate their way across the world's oceans in the 18th and 19th century. It also demonstrates the skill and workmanship of the early instrument makers that operated from London at this time and provided most of the navigational instrumentation use by commercial and military navies of the time.Octant, ebony wooden frame and handle. Scale is missing from recess in frame. "H. Hemsley 135-138 Ratliff Highway, London", no box"H. Hemsley 135-138 Ratcliff Highway, London"flagstaff hill, warrnambool, shipwrecked-coast, flagstaff-hill, flagstaff-hill-maritime-museum, maritime-museum, shipwreck-coast, flagstaff-hill-maritime-village, navigation, navigational instrument, instrument used for navigation, sextant, henry hemsley, instrument maker, london, octant