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instrument the distance of the star from the moon's limb; and though the instrument shake by the motion of the ship at sea, yet the moon and star will move together as if they did really touch one another in the heavens; so that an observation may be made as exactly at sea as at land. And by the same instrument, may be observed exactly the altitudes of the moon and stars, by bringing them to the horizon; and thereby the latitude and times of observation may be determined more exactly than by the ways now in use.
379:
489:
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195:
316:
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191:(G). This mirror was small enough to allow the observer to see the image in the mirror on one side and to see directly ahead on the other. The index arm (CD) held an index mirror (H), also at 45° to the edge of the index arm. The reflective sides of the two mirrors nominally faced each other, so that the image seen in the first mirror is that reflected from the second.
27:
724:
By this instrument the distance of the moon from any fixed star is thus observed; view the star through the perspicil by the direct light, and the moon by the reflexed, (or on the contrary;) and turn the index till the star touch the limb of the moon, and the index shall show on the brass limb of the
476:
glass mirrors with flat, parallel surfaces was limited. As glass polishing techniques improved, glass mirrors began to be provided. These used coatings of mercury-containing tin amalgam; coatings of silver or aluminum were not available until the 19th century. The poor optical quality of the early
427:
Various design elements of Smith's instrument made it inferior to Hadley's octant and it was not used significantly. For example, one problem with the
Astroscope was that angle of the observer's line of sight. By looking down, he had greater difficulty in observing than an orientation with his head
207:
reflects an image that is in a direction away from the direct line of sight. As the index arm movement increases, the line of sight for the index mirror moves toward S (to the right in the detail image). This shows a slight deficiency with this mirror arrangement. The horizon mirror will block the
172:
with 90 divisions of a half-degree each. Each such division was subdivided into 60 parts and each part further divided into sixths. This results in the arc being marked in degrees, minutes and sixths of a minute (10 seconds). Thus the instrument could have readings interpolated to 5 seconds of arc.
334:
were provided. The upper mirror, in the line of the sighting telescope, was small enough to allow the telescope to see directly ahead as well as seeing the reflected view. The reflected view was that of the light from the index mirror. As in the previous instrument, the arrangement of the mirrors
299:
Observing through the telescope, the navigator would sight one object directly ahead. The second object would be seen by reflection in the horizon mirror. The light in the horizon mirror is reflected from the index mirror. By moving the index arm, the index mirror can be made to reveal any object
342:
The second horizon mirror was an interesting innovation. The telescope was removable. It could be remounted so that the telescope viewed the second horizon mirror from the opposite side of the frame. By mounting the two horizon mirrors at right angles to each other and permitting the movement of
568:
These octants were available with many options. A basic octant with graduations directly on the wood frame were least expensive. These dispensed with a telescopic sight, using a single- or double-holed sighting pinnula instead. Ivory scales would increase the price, as would the use of a brass
513:
while the backstaff appeared to be accurate to one minute. The use of the vernier scale allowed the scale to be read to one minute, so improved the marketability of the instrument. This and the ease in making verniers compared to transversals, lead to adoption of the vernier on octants produced
295:
was mounted on the frame in the line of sight of the telescope. The horizon mirror allows the observer to see the image of the index mirror in one half of the view and to see a distant object in the other half. A shade was mounted at the vertex of the instrument to allow one to observe a bright
440:
Octant reverse side. This side is not seen in photographs very often. On the right, the thumbscrew to adjust the horizon mirror can be seen. At the top, one of the feet on which the octant rests in its case is just below the index arm axis. On the left the notepad is clearly visible. This small
657:
invented a reflecting quadrant in 1684 and had written about the concept as early as 1666. Hooke's was a single-reflecting instrument. Other octants were developed by Jean-Paul Fouchy and Caleb Smith in the early 1730s, however, these did not become significant in the history of navigation
598:
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
517:
Octants were produced in large numbers. In wood and ivory, their relatively low price compared to an all-brass sextant made them a popular instrument. The design was standardized with many manufacturers using the identical frame style and components. Different shops could make different
202:
With the two mirrors parallel, the index reads 0°. The view through the telescope sees directly ahead on one side and the view from the mirror G sees the same image reflected from mirror H (see detail drawing to the right). When the index arm is moved from zero to a large value, the
492:
Details on an octant. This photo shows the graduated scale and the end of the index arm with the vernier. The thumbscrew used to lock the index arm position is seen below the index arm while the thumbscrew used for fine adjustment of the arm is on the left. To the right of the value
251:. 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 century.
448:
The sight was easy to align because the horizon and the star seem to move together as the ship pitched and rolled. This also created a situation where the error in observation was less dependent on the observer, as they could directly see both objects at once.
335:
allowed the observer to simultaneously see an object straight ahead and to see one reflected in the index mirror to the horizon mirror and then into the telescope. Moving the index arm allowed the navigator to see any object within 90° of the direct view.
343:
the telescope, the navigator could measure angles from 0 to 90° with one horizon mirror and from 90° to 180° with the other. This made the instrument very versatile. For unknown reasons, this feature was not implemented on octants in general use.
626:
instruments were produced for use aboard aircraft. All were fitted with an artificial horizon in the form of a bubble, which was centered to align the horizon for a navigator flying thousands of feet above the Earth; some had recording features.
147:, but the description was not published until after Halley's death in 1742. It is not known why Halley did not publish the information during his life, as this prevented Newton from getting the credit for the invention that is generally given to
540:
Examples of these very similar octants are in the photos in this article. The image at the top is essentially the same instrument as the one in the detail photos. However, they are from two different instrument makers - the upper is labelled
556:
Octant details showing the double-holed sighting pinnula. Also visible is the small cover that can block one or the other of the holes. The horizon mirror is on the opposite side of the instrument. The left side is transparent while the
452:
With the use of the manufacturing techniques available in the 18th century, the instruments were capable of reading very accurately. The size of the instruments was reduced with no loss of accuracy. An octant could be half the size of a
338:
The significant difference with this design was that the mirrors allowed the instrument to be held vertically rather than horizontally and it provided more room for configuring the mirrors without suffering from mutual interference.
223:, produced an objectionable degree of aberration, so much so that it could affect the perception of a star's position. Long focal lengths were the solution, and this telescope would likely have had both a long–focal length
696:"A true Copy of a Paper found, in the Hand Writing of Sir Isaac Newton, among the Papers of the late Dr. Halley, containing a Description of an Instrument for observing the Moon's distance from the Fixt Stars at Sea"
460:
Using shades over the light paths, one could observe the sun directly, while moving the shades out of the light path allowed the navigator to observe faint stars. This made the instrument usable both night and day.
518:
components, with woodworkers specializing in frames and others in the brass components. For example, Spencer, Browning and Rust, a manufacturer of scientific instruments in
England from 1787 to 1840 (operating as
606:, 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 where it performs well.
564:
on the mirrored side has completely corroded and no longer reflects light. The back of the index mirror's holder is at the top and the three circular glass shades in square frames are between the two mirrors.
254:
Two others who created octants during this period were Caleb Smith, an
English insurance broker with a strong interest in astronomy (in 1734), and Jean-Paul Fouchy, a mathematics professor and astronomer in
587:, 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,
497:
on the main scale, the SBR logo is engraved. The scale is directly graduated in degrees and thirds of a degree (20'). The vernier can divide the 20' intervals to the nearest minute of arc.
472:
Early octants were constructed primarily in wood, with later versions incorporating ivory and brass components. The earliest mirrors were polished metal, since the technology to produce
95:
derives from the instrument using mirrors to reflect the path of light to the observer and, in doing so, doubles the angle measured. This allows the instrument to use a one-eighth of a
158:
One copy of this instrument was constructed by Thomas Heath (instrument maker) and may have been shown in Heath's shop window prior to its being published by the Royal
Society in 1742.
198:
Details of the mirrors on Newton's reflecting quadrant, showing the light paths (red) through the instrument. This image is turned 90° anticlockwise relative to the one above.
300:
up to 90° from the direct line of sight. When both objects are in the same view, aligning them together allows the navigator to measure the angular distance between them.
211:
The length of the sighting telescope seems remarkable, given the small size of the telescopes on modern instruments. This was likely Newton's choice of a way to reduce
386:
346:
Comparing this instrument to the photo of a typical octant at the top of the article, one can see that the only significant differences in the more modern design are:
602:
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
599:
instrument. The lower price of the octant, including versions without telescope, made it a practical instrument for ships in the merchant and fishing fleets.
323:
Hadley's second design had the form familiar to modern navigators. The image to the right, also taken from his Royal
Society publication, shows the details.
1089:
412:
In the drawing to the right, the horizon element (B) could be a mirror or a prism. On the index arm, the index mirror (A) rotated with the arm. A sighting
173:
This fineness of graduation is only possible due to the large size of the instrument - the sighting telescope alone was three to four feet long.
1423:
283:
Hadley's first reflecting quadrant was a simple device with a frame spanning a 45° arc. In the image at the right, from Hadley's article in the
46:
and signature plate. The index arm and mirror supports are brass. Rather than use a sighting telescope, this instrument has a sighting pinnula.
2361:
1241:
161:
Newton's instrument used two mirrors, but they were used in an arrangement somewhat different from the two mirrors found in modern octants and
356:
The position of the shades for the index mirror is in the path between the index and horizon mirrors rather than at the top of the instrument.
1991:
416:
was mounted on the frame (C). The index did not use a vernier or other device at the scale (D). Smith called the instrument's index arm a
287:
of the Royal
Society, you can see the nature of his design. A small sighting telescope was mounted on the frame along one side. One large
1150:
865:
1216:
2367:
1082:
303:
Very few of the original reflecting quadrant designs were ever produced. One, constructed by
Baradelle, is in the collection of the
481:
mirrors meant that telescopic sights were not practical. For that reason, most early octants employed a simple naked-eye sighting
2140:
1098:
1895:
916:
Bennett, Jim, "Catadioptrics and commerce in eighteenth-century London", in
History of Science, vol xliv, 2006, pages 247-277.
401:
in addition to an index mirror to provide reflective elements. Prisms provide advantages over mirrors in an era when polished
1916:
1666:
982:
852:
996:
2538:
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212:
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1803:
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1737:
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974:
954:
934:
905:
752:
275:
Hadley produced two versions of the reflecting quadrant. Only the second is well known and is the familiar octant.
1767:
1757:
667:
549:. The only obvious difference is the presence of horizon shades on the Crichton octant that are not on the other.
441:
keystone-shaped piece of ivory, scarcely larger than a thumbnail, was used by the navigator to record his readings.
389:, an English insurance broker with a strong interest in astronomy, had created an octant in 1734. He called it an
2533:
506:
1625:
1560:
362:
Separate shades are provided on the horizon mirror for sighting a low sun position with a very bright horizon.
2548:
1676:
740:
591:, who conducted shipboard experiments with the lunar distance method, suggested a larger instrument and the
1793:
1701:
1580:
1165:
2356:
2235:
2109:
1155:
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on the scale. However, as engraved, they showed the instrument to have an apparent accuracy of only two
143:'s reflecting quadrant was invented around 1699. A detailed description of the instrument was given to
271:
Hadley's reflecting quadrant. This instrument follows the form of Newton's reflecting quadrant from 1699
2467:
1610:
1600:
1221:
1111:
464:
By 1780, the octant and sextant had almost completely displaced all previous navigational instruments.
1231:
1877:
1458:
1342:
584:
244:
152:
783:
1691:
1585:
1463:
1226:
1186:
1062:
588:
1681:
778:
1696:
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1307:
1297:
1236:
672:
530:
169:
2114:
2074:
1888:
1829:
1788:
1615:
1595:
1514:
1392:
877:
2381:
2175:
2089:
1762:
1575:
1544:
1489:
1277:
1043:
The
Mariner's Sextant and the Royal Society; Notes and Records of the Royal Society of London
648:
603:
62:
57:
799:
695:
304:
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2215:
2185:
1590:
1570:
1261:
1160:
1145:
707:
579:
1067:
620:
From the early 1930s through the end of the 1950s, several types of civilian and military
8:
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2094:
1950:
1909:
1630:
1605:
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1211:
561:
421:
1256:
772:
711:
2405:
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2024:
1976:
1834:
1387:
1181:
893:
821:
728:
636:
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object. The shade pivots to allow it to move out of the way for stellar observations.
220:
2436:
2431:
2305:
2165:
1706:
1640:
1635:
1352:
978:
970:
950:
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901:
848:
825:
748:
552:
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of a mirror and the production of glass with flat, parallel surfaces was difficult.
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2446:
2415:
2290:
2280:
2210:
2069:
2029:
2014:
1937:
1902:
1882:
1824:
1747:
1732:
1727:
1453:
1302:
1191:
845:
Scientific
Instruments of the Seventeenth and Eighteenth Centuries and Their Makers
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715:
1000:
2351:
2285:
2049:
2004:
1534:
1408:
1377:
1327:
1312:
1140:
526:
267:
120:
104:
100:
96:
1367:
183:(AB), three or four feet long, was mounted along one side of the instrument. A
16:
Measuring instrument used primarily in navigation; type of reflecting instrument
2493:
2195:
2170:
1956:
1819:
1473:
1448:
1433:
1418:
1382:
1251:
768:
510:
478:
454:
402:
398:
319:
Hadley's Octant. This is in the form familiar to those who have seen a sextant.
224:
188:
350:
The location of the horizon mirror and telescope or sighting pinnula is lower.
2527:
2315:
2225:
2099:
1969:
1962:
1661:
1529:
1443:
1018:
622:
615:
523:
144:
43:
1504:
745:
The Haven-finding Art: A History of Navigation from Odysseus to Captain Cook
2505:
2145:
2039:
1752:
1686:
1539:
1282:
1246:
816:
719:
691:
654:
248:
216:
140:
378:
2320:
2310:
2275:
2084:
2064:
1943:
1783:
1519:
1468:
1428:
1196:
488:
291:
was mounted at the point of rotation of the index arm. A second, smaller
240:
194:
148:
2265:
2255:
2245:
2150:
2130:
2054:
1722:
1671:
1509:
1499:
1337:
1332:
1317:
165:. The diagram on the right shows the configuration of the instrument.
66:
2488:
445:
The octant provided a number of advantages over previous instruments.
2300:
2240:
2019:
1798:
1742:
1413:
1347:
1322:
1206:
502:
473:
413:
406:
179:
900:, G. T. Foulis & Co. Ltd., Henley-on-Thames, Oxfordshire, 1973,
315:
231:. This would decrease aberrations without excessive magnification.
2325:
2295:
2260:
2250:
2190:
2009:
1524:
1494:
1438:
1372:
1362:
1287:
1201:
228:
774:
Memoirs of the Life, Writings, and Discoveries of Sir Isaac Newton
537:
initials could be found on octants from many other manufacturers.
359:
Multiple shades are used to allow for different levels of shading.
2230:
2220:
2155:
2104:
2044:
2034:
1999:
1357:
635:
Use and adjustment of the octant is essentially identical to the
592:
482:
436:
366:
162:
20:
2205:
2200:
1057:
256:
777:. Vol. 1. Edinburgh: Thomas Constable & Co. pp.
2270:
2135:
2059:
353:
The internal bracing of the frame is more central and robust.
39:
35:
1097:
533:
scales in ivory. These were widely used by others and the
2500:
89:, because the instrument's arc is one eighth of a circle.
1928:
558:
26:
866:"History Corner: Benjamin King of Newport, R.I.-Part II"
239:
Two men independently developed the octant around 1730:
800:"The Description of a new Instrument for taking Angles"
501:
Early octants retained some of the features common to
2465:
187:
was fixed at a 45° angle in front of the telescope's
208:
view of the index mirror at angles approaching 90°.
545:while the detail images are of an instrument from
653:Hadley's was not the first reflecting quadrant.
2525:
804:Philosophical Transactions of the Royal Society
700:Philosophical Transactions of the Royal Society
642:
278:
115:
234:
124:Drawing of Newton's Reflecting Quadrant. From
1083:
793:
791:
382:Drawing of Smith's Astroscope or Sea-quadrant
32:Crichton - London, Sold by J Berry, Aberdeen
543:Crichton - London, Sold by J Berry Aberdeen
467:
431:
365:The second horizon mirror and accompanying
243:(1682–1744), an English mathematician, and
1090:
1076:
1045:, Vol. 33, No. 1 (August 1978), pp. 23-36.
788:
23:, a similar type of reflecting instrument.
1037:
1035:
947:Nineteenth Century Scientific Instruments
815:
967:Lost Star: The Search for Amelia Earhart
839:
837:
835:
767:
733:
551:
487:
435:
377:
314:
266:
219:telescopes, prior to the development of
193:
168:The 45° arc of the instrument (PQ), was
128:, p. 243). AB – sighting telescope
125:
119:
25:
1099:Astronomy in the medieval Islamic world
994:
572:
110:
2526:
1896:Encyclopedia of the Brethren of Purity
1242:Khalid ibn Abd al‐Malik al‐Marwarrudhi
1032:
969:, W. W. Norton & Company, (1994),
939:
910:
863:
798:Hadley, John (August–September 1731).
797:
739:
690:
1917:The Remaining Signs of Past Centuries
1855:
1109:
1071:
889:
887:
857:
832:
630:
373:
1866:
262:
1015:"Chronology of Robert Hooke's life"
925:Harriet Wynter and Anthony Turner,
405:mirrors were inferior and both the
13:
884:
547:Spencer, Browning & Co. London
310:
30:Octant. This instrument, labelled
14:
2560:
1051:
864:Bedini, Silvio (September 1997).
420:, in the manner of Elton for his
2511:
2499:
2487:
2475:
1123:
1056:
668:List of astronomical instruments
609:
1621:Muhammad ibn Abi Bakr al‐Farisi
1110:
1007:
988:
959:
747:. London: Hollis & Carter.
2110:Schema for horizontal sundials
1626:Abu Ali al-Hasan al-Marrakushi
1151:Muḥammad ibn Ibrāhīm al-Fazārī
949:, Sotheby Publications, 1983,
919:
898:A History of Marine Navigation
870:Professional Surveyor Magazine
847:, Portman Books, London 1989
761:
684:
1:
678:
577:In 1767 the first edition of
2368:Constantinople (Taqi al-Din)
643:Other reflecting instruments
279:Hadley's reflecting quadrant
116:Newton's reflecting quadrant
72:
7:
2539:Angle measuring instruments
2357:University of al-Qarawiyyin
1561:Ibn al-Banna' al-Marrakushi
810:(420): 147–157 and plates.
661:
514:later in the 18th century.
457:with no increase in error.
235:The inventors of the octant
10:
2565:
1856:
1601:Shams al-Din al-Samarqandi
997:"Evolution of the Sextant"
706:(465): 155–156 and plate.
646:
613:
285:Philosophical Transactions
247:(1704–1749), a glazier in
18:
2442:Medieval European science
2424:
2393:
2334:
2123:
1990:
1926:
1873:
1862:
1851:
1812:
1776:
1715:
1702:Sadr al-Shari'a al-Asghar
1654:
1553:
1482:
1459:Ibrahim ibn Said al-Sahli
1401:
1270:
1174:
1133:
1122:
1118:
1105:
694:(October–November 1742).
520:Spencer, Browning and Co.
428:in a normal orientation.
2544:Astronomical instruments
1692:Nizam al-Din al-Nisapuri
1586:Muhyi al-Din al-Maghribi
1227:Ali ibn Isa al-Asturlabi
569:index arm or a vernier.
468:Production of the octant
432:Advantages of the octant
227:and a long–focal length
19:Not to be confused with
1794:Baha' al-din al-'Amili
1768:'Abd al-'Aziz al-Wafa'i
1646:Fakhr al-Din al-Akhlati
1566:Ibn al‐Ha'im al‐Ishbili
929:, Studio Vista, 1975,
673:Octant (plane geometry)
330:on the index arm. Two
87:eighth part of a circle
81:derives from the Latin
2534:Navigational equipment
2075:Navigational astrolabe
1830:Al Achsasi al Mouakket
1596:Qutb al-Din al-Shirazi
1515:Al-Samawal al-Maghribi
1464:Ibn Mu'adh al-Jayyani
1393:Abu al-Hasan al-Ahwazi
927:Scientific Instruments
817:10.1098/rstl.1731.0025
729:Vol. 42 at archive.org
720:10.1098/rstl.1742.0039
565:
498:
442:
383:
320:
272:
199:
137:
47:
2411:Hellenistic astronomy
2382:Samarkand (Ulugh Beg)
2176:Deferent and epicycle
1576:Alam al-Din al-Hanafi
1545:Sharaf al-Din al-Tusi
1187:Abu Ma'shar al-Balkhi
1065:at Wikimedia Commons
995:Cardoza, Rod (n.d.).
649:Reflecting instrument
589:Admiral John Campbell
555:
491:
439:
381:
318:
270:
213:chromatic aberrations
197:
123:
99:to measure a quarter-
63:reflecting instrument
34:, appears to have an
29:
2549:Celestial navigation
2401:Babylonian astronomy
2216:Gravitational energy
1591:Nasir al-Din al-Tusi
1581:Najm al‐Din al‐Misri
1262:Yahya ibn Abi Mansur
1161:Mashallah ibn Athari
1146:Al-Fadl ibn Naubakht
945:Gerard L'E. Turner,
580:The Nautical Almanac
573:Demise of the octant
397:. His used a fixed
111:Origin of the octant
2342:Al-Azhar University
2161:Celestial mechanics
1951:Book of Fixed Stars
1910:The Book of Healing
1889:Aja'ib al-Makhluqat
1631:Ibn Ishaq al-Tunisi
1606:Zakariya al-Qazwini
1217:Al-Ḥajjāj ibn Yūsuf
1212:Abu Hanifa Dinawari
894:May, William Edward
876:(6). Archived from
712:1742RSPT...42..155N
637:navigator's sextant
522:after 1840) used a
93:Reflecting quadrant
2406:Egyptian astronomy
2347:House of Knowledge
2025:Astronomical clock
1835:Muhammad al-Rudani
1232:Banū Mūsā brothers
1182:Abu Ali al-Khayyat
1041:Charles H. Cotter
843:Daumas, Maurice,
631:Use and adjustment
566:
499:
443:
422:mariner's quadrant
384:
374:Smith's Astroscope
321:
305:Musée de la Marine
273:
200:
138:
136:PQ – graduated arc
132:G – horizon mirror
48:
2463:
2462:
2459:
2458:
2455:
2454:
2437:Chinese astronomy
2432:Byzantine science
2306:Temporal finitism
2236:Islamic cosmology
2166:Celestial spheres
1986:
1985:
1878:Arabic star names
1847:
1846:
1843:
1842:
1707:Fathullah Shirazi
1641:Al-Ashraf Umar II
1353:Ibrahim ibn Sinan
1156:Ibrāhīm al-Fazārī
1061:Media related to
983:978-0-393-02683-2
853:978-0-7134-0727-3
263:Hadley's versions
221:achromatic lenses
2556:
2516:
2515:
2514:
2504:
2503:
2492:
2491:
2480:
2479:
2478:
2471:
2447:Indian astronomy
2416:Indian astronomy
2384:
2377:
2370:
2291:Sublunary sphere
2281:Specific gravity
2181:Earth's rotation
2070:Mural instrument
2015:Armillary sphere
1938:Alfonsine tables
1903:Tabula Rogeriana
1883:Islamic calendar
1871:
1870:
1864:
1863:
1853:
1852:
1748:Sibt al-Maridini
1733:Jamshid al-Kashi
1454:Said al-Andalusi
1257:Thābit ibn Qurra
1192:Abu Said Gorgani
1166:Yaʿqūb ibn Ṭāriq
1120:
1119:
1107:
1106:
1092:
1085:
1078:
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1046:
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1017:. Archived from
1011:
1005:
1004:
999:. Archived from
992:
986:
965:Brink, Randall,
963:
957:
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758:
741:Taylor, E. G. R.
737:
731:
727:
688:
369:is not provided.
134:H – index mirror
54:, also called a
2564:
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2555:
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2373:
2366:
2352:House of Wisdom
2330:
2286:Spherical Earth
2119:
2050:Equatorial ring
2030:Celestial globe
2005:Analog computer
1982:
1977:Sullam al-sama'
1922:
1858:
1839:
1808:
1772:
1711:
1650:
1549:
1535:Jabir ibn Aflah
1478:
1409:Abu Nasr Mansur
1397:
1378:Abolfadl Harawi
1313:Ahmad ibn Yusuf
1266:
1170:
1141:Ahmad Nahavandi
1129:
1114:
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796:
789:
769:Brewster, David
766:
762:
755:
738:
734:
689:
685:
681:
664:
651:
645:
633:
618:
612:
595:was developed.
585:lunar distances
575:
527:dividing engine
470:
434:
376:
332:horizon mirrors
313:
311:Hadley's octant
281:
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237:
135:
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75:
24:
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2196:Elliptic orbit
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2171:Circular orbit
2168:
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2158:
2153:
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2017:
2012:
2007:
2002:
1996:
1994:
1988:
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1984:
1983:
1981:
1980:
1973:
1966:
1959:
1957:Toledan Tables
1954:
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1820:Yang Guangxian
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1507:
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1497:
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1486:
1484:
1480:
1479:
1477:
1476:
1474:Ali ibn Khalaf
1471:
1466:
1461:
1456:
1451:
1449:Kushyar Gilani
1446:
1441:
1436:
1431:
1426:
1421:
1419:Ali ibn Ridwan
1416:
1411:
1405:
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1383:Haseb-i Tabari
1380:
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1254:
1252:Sahl ibn Bishr
1249:
1244:
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1234:
1229:
1224:
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1199:
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1102:
1095:
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1087:
1080:
1072:
1053:
1052:External links
1050:
1048:
1047:
1031:
1006:
1003:on 2008-07-26.
987:
958:
938:
918:
909:
883:
880:on 2006-11-21.
856:
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647:Main article:
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614:Main article:
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511:minutes of arc
479:speculum metal
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455:Davis quadrant
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403:speculum metal
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293:horizon mirror
280:
277:
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261:
245:Thomas Godfrey
236:
233:
225:objective lens
189:objective lens
185:horizon mirror
153:Thomas Godfrey
130:CD – index arm
126:Brewster (1855
117:
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2362:Observatories
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2226:Heliocentrism
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2100:Shadow square
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1970:Zij-i Sultani
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1738:Kadızade Rumi
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1662:Ibn al-Shatir
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1636:Ibn al‐Raqqam
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1530:Ibn al-Kammad
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1444:Ibn al-Saffar
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1036:
1021:on 2012-04-14
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975:0-393-02683-3
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935:0-289-70403-0
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906:0-85429-143-1
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692:Newton, Isaac
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623:bubble octant
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2518:Solar System
2335:Institutions
2186:Eccentricity
2146:Astrophysics
2079:
2040:Compass rose
1975:
1968:
1961:
1949:
1942:
1927:
1915:
1908:
1901:
1894:
1887:
1753:Ibn al-Majdi
1728:Abd al‐Wajid
1687:Al-Wabkanawi
1682:Abū al‐ʿUqūl
1571:Jamal ad-Din
1540:Omar Khayyam
1368:Al-ʻIjliyyah
1343:Aṣ-Ṣaidanānī
1328:Ibn al-A'lam
1247:Al-Khwarizmi
1055:
1042:
1023:. Retrieved
1019:the original
1009:
1001:the original
990:
966:
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941:
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878:the original
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655:Robert Hooke
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507:transversals
500:
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395:Sea-Quadrant
394:
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328:index mirror
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289:index mirror
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249:Philadelphia
238:
217:focal length
210:
205:index mirror
204:
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184:
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141:Isaac Newton
139:
92:
91:
86:
82:
78:
76:
55:
51:
49:
31:
2321:Tusi couple
2311:Trepidation
2276:Salah times
2211:Geocentrism
2085:Planisphere
2065:Graph paper
1992:Instruments
1944:Huihui Lifa
1825:Ehmedê Xanî
1784:Al-Birjandi
1763:al-Kubunani
1520:Abu al-Salt
1469:Al-Isfizari
1429:Ibn al-Samh
1308:Abu al-Wafa
1293:al-Khojandi
1197:Al-Farghani
1112:Astronomers
529:to produce
387:Caleb Smith
259:(in 1732).
241:John Hadley
149:John Hadley
56:reflecting
38:frame with
2528:Categories
2425:Influenced
2394:Influences
2266:Precession
2246:Multiverse
2151:Axial tilt
2131:Almucantar
2115:Triquetrum
2055:Equatorium
1804:Takiyüddin
1677:al-Battiwi
1672:Ibn Shuayb
1667:Al-Khalili
1510:Al-Khazini
1505:Al-Kharaqī
1500:Ibn Tufail
1490:Al-Bitruji
1424:Al-Zarqālī
1388:al-Majriti
1338:Al-Saghani
1333:Al-Nayrizi
1318:al-Battani
1237:Iranshahri
1222:Al-Marwazi
1126:by century
1025:2007-09-13
679:References
583:tabulated
505:, such as
503:backstaves
391:Astroscope
67:navigation
2482:Astronomy
2301:Supernova
2256:Obliquity
2241:Moonlight
2141:Astrology
2020:Astrolabe
1799:Piri Reis
1789:al-Khafri
1758:al-Wafa'i
1743:Ulugh Beg
1723:Ali Kuşçu
1697:al-Jadiri
1616:al-Abhari
1414:al-Biruni
1348:Ibn Yunus
1323:Al-Qabisi
1298:al-Khazin
1207:Al-Mahani
826:186212825
531:graduated
485:instead.
477:polished
414:telescope
407:silvering
307:, Paris.
215:. Short–
180:telescope
178:sighting
170:graduated
77:The name
73:Etymology
2375:Maragheh
2326:Universe
2296:Sunlight
2261:Parallax
2251:Muwaqqit
2191:Ecliptic
2124:Concepts
2090:Quadrant
2010:Aperture
1525:Averroes
1495:Avempace
1439:Avicenna
1373:Nastulus
1363:al-Sijzi
1288:Al-Adami
1202:Al-Kindi
771:(1855).
743:(1971).
662:See also
474:silvered
229:eyepiece
163:sextants
105:quadrant
85:meaning
65:used in
58:quadrant
2494:Science
2468:Portals
2231:Inertia
2221:Gravity
2156:Azimuth
2105:Sundial
2095:Sextant
2045:Dioptra
2035:Compass
2000:Alidade
1611:al-Urdi
1434:Alhazen
1358:Ma Yize
1303:al-Qūhī
1278:al-Sufi
1063:Octants
985:, p. 32
784:excerpt
708:Bibcode
593:sextant
562:amalgam
524:Ramsden
483:pinnula
367:alidade
61:, is a
44:vernier
42:scale,
21:Sextant
2206:Galaxy
2201:Equant
2136:Apogee
2080:Octant
1857:Topics
981:
973:
953:
933:
904:
851:
824:
751:
604:lunars
257:France
83:octans
79:octant
52:octant
2506:Stars
2271:Qibla
2060:Globe
1867:Works
822:S2CID
781:–242.
418:label
399:prism
40:ivory
36:ebony
1813:17th
1777:16th
1716:15th
1655:14th
1554:13th
1483:12th
1402:11th
1271:10th
979:ISBN
971:ISBN
951:ISBN
931:ISBN
902:ISBN
849:ISBN
749:ISBN
151:and
101:turn
97:turn
50:The
1929:Zij
1283:Ibn
1175:9th
1134:8th
812:doi
779:239
716:doi
559:tin
535:SBR
393:or
103:or
2530::
1034:^
977:,
896:,
886:^
874:17
872:.
868:.
834:^
820:.
808:37
806:.
802:.
790:^
722:.
714:.
704:42
702:.
698:.
639:.
495:50
424:.
176:A
155:.
107:.
69:.
2470::
1091:e
1084:t
1077:v
1028:.
828:.
814::
757:.
718::
710::
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