This representative example demonstrates a mariner’s astrolabe. Historical examples are rare. There are less than one hundred known to exist and most of these have been recovered from shipwrecks, many from Spanish and Portuguese vessels. An astrolabe is a measuring device once used to navigate the seas by observing the sun and stars to measure their altitude. The measurement of altitude could then be used to calculate the ship’s latitude but at that time in history there was no means of measuring longitude. The body of the navigational astrolabe was cast brass and much heavier, and less complicated than the variety used on land. The heavier weight and cut-away shape reduced the effect of the wind and waves when trying to use it at sea. A mariner’s astrolabe or ‘star finder’ is a simplified version than that used by Arabic astronomers to find the altitude of the sun and stars above the horizon, and time of the sunrise and sunset. It is a forerunner to the quadrant, octant and sextant and was popular for about 200 years over the 1500s and 1600s to find the latitude of a ship at sea. The user held the astrolabe at eye level and, usually with assistance, aligned the stars through the two small sights (pinnules), then read the altitude indicated by the pointer on the arm. It could also be used to sight the sun by holding it lower down, aiming it at the sun, and adjusting it until the sun shone through both pinnules. This astrolabe is an example used to demonstrate the mariner’s astrolabe, which was navigational tool of the 1500s and 1600s, in the time before longitude was able to be determined. It is a forerunner to modern navigation technology. Mariner’s astrolabe – a representative example. A gold painted, disc shaped object with cut outs and revolving arm in centre. The arm has two sights attached at right angles. The top has a ring attached. Measurements are marked in degrees in a circular scale around outer edge.flagstaff hill, warrnambool, maritime village, maritime museum, flagstaff hill maritime museum & village, shipwreck coast, great ocean road, navigation instrument, navigation tool, navigation, astrolabe, mariner’s astrolabe, measure latitude, measure altitude, arabic navigation, measuring device, star finder, astronomy, marine tool, marine instrument

A sextant is an instrument generally used to measure the altitude of a celestial object above the horizon. Sextant with a black timber (ebony?) frame, ivory graduated scales and brass attachments : vernier scale radial arm, mirrors and optical filterssextant, astronomy, scientific object, scientific instruments

Bubble Sextant model Mark 1XA type A.M. 6B/218 in protective storage box. Complete, with operation instructions. This is an aviation navigation instrument used by the RAF and RAAF during the World War 2 era. A sextant is used to measure the altitude of celestial bodies above a horizontal line of reference. A navigator can use the horizon as this line of reference, but when an aircraft is above the clouds or flying at night, the navigator can’t see the horizon. The bubble sextant solves this problem by providing an artificial horizon.The storage case has a label with the following: "A.M. 6B/218 MK IX A" and the number "10772/42 (V)"

The theodolite was sold by T. Gaunt & Co. of Melbourne, a manufacturer, importer and retailer of a wide variety of goods including jewellery, clocks and watches, navigational and measuring instruments, dinnerware, glassware and ornaments. Thomas Gaunt photograph was included in an album of security identity portraits of members of the Victorian Court, Centennial International Exhibition, Melbourne, 1888. (See further details below.) History for Troughton & Simms: Edward Troughton & William Simms established a scientific instrument making business in London in 1826. Edward Troughton (1756-1835) had previously had his own scientific instrument business, inherited from his father. His achievement's included a transit telescope for Greenwich Observatory (1816) and the precision surveying instruments for the Ordnance Survey of Britain, Ireland and India. William Simms (1793-1860) had trained as a goldsmith and began to gain work dividing circles on fine astronomical instruments. When William Simms died in 1860, the business was taken over by his son James and nephew William. Troughton & Simms shop in Fleet Street became the hub of the finest scientific instrument made in London, in a period in which there was an expanding demand for precision instruments, for astronomy, surveying and precision measurement. They made instruments for Greenwich Observatory, for imperial surveys and exploring expeditions. When fire destroyed the Houses of Parliament in 1834, the firm was commissioned to create new standard lengths, this required 10 years of testing against the remaining old measurements. Troughton and Simms made several of the main instruments for Melbourne Observatory, including an 18 inch azimuth used of the Geodetic Survey, portable transit instrument (circa 1850), zenith sector (1860), a 4.5 inch equatorial telescope (1862), an 8 inch equatorial telescope (1874) spectroscope (1877) and an 8 inch transit instrument in (1884). While the firm had an excellent reputation for quality the company exasperated many of its customers with delays of years in delivering some instruments. History for Thomas Gaunt: Thomas Ambrose Gaunt (1829 – 1890) was a jeweller, clock maker, and manufacturer of scientific instruments, whose head office and showroom were at 337–339 Bourke Street, Melbourne, Victoria, Australia. Thomas Gaunt established Melbourne's leading watchmaking, optical and jewellery business during the second half of the 19th century. Gaunt arrived in Melbourne in 1852, and by 1858 had established his own business at 14 Little Bourke Street. Around 1869 he moved to new premises in Bourke Street on the corner of Royal Arcade, Gaunt's shop quickly became a Melbourne institution. Gaunt proudly advertised that he was 'The only watch manufacturer in the Australian colonies'. While many watches and clocks may have had Gaunt's name on the dial, few would have been made locally. Gaunt did make some watches for exhibitions, and perhaps a few expensive watches for wealthy individuals. Gaunt's received a telegraph signal from Melbourne Observatory each day to correct his main clock and used this signal to rate and repair ship's chronometers and good quality watches. Thomas Gaunt also developed a department that focused on scientific instrumentation, making thermometers and barometers (from imported glass tubes), telescopes, surveying instruments and microscopes. Significance: With the rapid urban expansion, one of the most important needs of the new colony was to survey and map the landscape of the Australian Colony’s interior. Theodolites, such as this one, made by Troughton and Simms, who were significant scientific instrument makers of the 19th century were instrumental to the colony's surveyors and would have played an important part in their everyday work. This transit theodolite remains of national significance due to its pioneering role in Australian science and its association with Australia's earliest surveyors and astronomers. It is also significant for its association with nineteenth-century surveying instruments and instrument makers. Theodolite, Vernier repetition theodolite with enclosed horizontal circle (of about 130 mm diameter). Vertical circle exposed and somewhat corroded (diameter about 115 mm). Plate level 20" per division. Altitude bubble 20" per division. Horizontal and vertical circle intervals 20". Original (blue/grey) paint. Altitude bubble setting screw disabled. Tribrach allows movement of theodolite by 15 mm inside tribrach (for centering).Inscribed on the inner mounting plate,“Specially made in England for T Gaunt & Co Melbourne” and inscribed a little lower “Troughton & Simms London”flagstaff hill, warrnambool, shipwrecked-coast, flagstaff-hill, flagstaff-hill-maritime-museum, maritime-museum, shipwreck-coast, flagstaff-hill-maritime-village, theodolite, t. gaunt & co, troughton & simms, scientific instrument, measuring instrument, surveyor's instrument

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

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