307:
303:, with which the distance of the circle graduations from the centre of the field of view could be measured. The drum of the screw was divided to measure single seconds of arc (0.1" being estimated), while the number of revolutions were counted by a comb like scale in the field of view. The microscopes were given such magnification and placed at such a distance from the circle that one revolution of the micrometer screw corresponded to 1 arcminute (1') on the circle. The error was determined occasionally by measuring standard intervals of 2' or 5' on the circle. The periodic errors of the screw were accounted for. On some instruments, one of the circles was graduated and read more coarsely than the other, and was used only in finding the target stars.
246:, either set into massive stone or brick piers which supported the instrument, or attached to metal frameworks on the tops of the piers. The temperature of the instrument and local atmosphere were monitored by thermometers. The piers were usually separate from the foundation of the building, to prevent transmission of vibration from the building to the telescope. To relieve the pivots from the weight of the instrument, which would have distorted their shape and caused rapid wear, each end of the axis was supported by a hook or yoke with
503:
203:
144:
1380:
1595:
842:
1619:
1571:
1607:
1583:
655:, Ptolemy describes a meridian circle which consisted of a fixed graduated outer ring and a movable inner ring with tabs that used a shadow to set the Sun's position. It was mounted vertically and aligned with the meridian. The instrument was used to measure the altitude of the Sun at noon in order to determine the path of the
668:
474:. The difference between the circle reading after observing a star and the reading corresponding to the zenith was the zenith distance of the star, and this plus the colatitude was the north polar distance. To determine the zenith point of the circle, the telescope was directed vertically downwards at a basin of
295:, generally four for each circle, mounted to the piers or a framework surrounding the axis, at 90° intervals around the circles. By averaging the four readings the eccentricity (from inaccurate centering of the circles) and the errors of graduation were greatly reduced. Each microscope was furnished with a
343:
separate piers. The meridian telescope was pointed to one collimator and then the other, moving through exactly 180°, and by reading the circle the amount of flexure (the amount the readings differed from 180°) was found. Absolute flexure, that is, a fixed bend in the tube, was detected by arranging that
781:
In the United
Kingdom, the transit instrument and mural circle continued until the middle of the 19th century to be the principal instrument in observatories, the first transit circle constructed there being that at Greenwich (mounted in 1850). However, on the continent, the transit circle superseded
358:
The observing building housing the meridian circle did not have a rotating dome, as is often seen at observatories. Since the telescope observed only in the meridian, a vertical slot in the north and south walls, and across the roof between these, was all that was necessary. The building was unheated
354:
Certain instrumental errors could be averaged out by reversing the telescope on its mounting. A carriage was provided, which ran on rails between the piers, and on which the axis, circles and telescope could be raised by a screw-jack, wheeled out from between the piers, turned 180°, wheeled back, and
350:
Parts of the apparatus, including the circles, pivots and bearings, were sometimes enclosed in glass cases to protect them from dust. These cases had openings for access. The reading microscopes then extended into the glass cases, while their eyepiece ends and micrometers were protected from dust by
527:
The line of sight of the telescope needed to be exactly perpendicular to the axis of rotation. This could be done by sighting a distant, stationary object, lifting and reversing the telescope on its bearings, and again sighting the object. If the crosshairs did not intersect the object, the line of
263:
was used to monitor for any inclination of the axis to the horizon. Eccentricity (an off-center condition) or other irregularities of the pivots of the telescope's axis was accounted for, in some cases, by providing another telescope through the axis itself. By observing the motion of an artificial
485:
was taken into account as well as the errors of graduation and flexure. If the bisection of the star on the horizontal wire was not made in the centre of the field, allowance was made for curvature, or the deviation of the star's path from a great circle, and for the inclination of the horizontal
1426:
The
Practical Astronomer: Comprising Illustrations of Light and Colours—practical Descriptions of All Kinds of Telescopes—the Use of the Equatiorial Transit, Circular, and Other Astronomical Instruments; a Particular Account of the Earl of Rosse's Large Telescopes and Other Topics Connected with
535:
The line of sight of the telescope needed to be exactly within the plane of the meridian. This was done approximately by building the piers and the bearings of the axis on an east–west line. The telescope was then brought into the meridian by repeatedly timing the (apparent, incorrect) upper and
493:
was placed in the focus of a transit instrument and a number of short exposures made, their length and the time being registered automatically by a clock. The exposing shutter was a thin strip of steel, fixed to the armature of an electromagnet. The plate thus recorded a series of dots or short
478:, the surface of which formed an absolutely horizontal mirror. The observer saw the horizontal wire and its reflected image, and moving the telescope to make these coincide, its optical axis was made perpendicular to the plane of the horizon, and the circle reading was 180° + zenith point.
426:
The vertical wires were used for observing transits of stars, each wire furnishing a separate result. The time of transit over the middle wire was estimated, during subsequent analysis of the data, for each wire by adding or subtracting the known interval between the middle wire and the wire in
342:
towards it. These were pointed at one another (through holes in the tube of the telescope, or by removing the telescope from its mount) so that the crosshairs in their foci coincided. The collimators were often permanently mounted in these positions, with their objectives and eyepieces fixed to
399:. By this slow motion, the telescope was adjusted until the star moved along the horizontal wire (or if there were two, in the middle between them), from the east side of the field of view to the west. Following this, the circles were read by the microscopes for a measurement of the apparent
540:
and adjusting one of the bearings horizontally until the interval between the transits was equal. Another method used calculated meridian crossing times for particular stars as established by other observatories. This was an important adjustment, and much effort was spent in perfecting it.
798:. The firm of Repsold and Sons was for a number of years eclipsed by that of Pistor and Martins in Berlin, who furnished various observatories with first-class instruments. Following the death of Martins, the Repsolds again took the lead and made many transit circles. The observatories of
258:
so as to leave only a small fraction of the weight on the precision V-shaped bearings. In some cases, the counterweight pushed up on the roller bearings from below. The bearings were set nearly in a true east–west line, but fine adjustment was possible by horizontal and vertical screws. A
532:, and the crosshairs illuminated. The mercury acted as a perfectly horizontal mirror, reflecting an image of the crosshairs back up the telescope tube. The crosshairs could then be adjusted until coincident with their reflection, and the line of sight was then perpendicular to the axis.
528:
sight was halfway between the new position of the crosshairs and the distant object; the crosshairs were adjusted accordingly and the process repeated as necessary. Also, if the rotation axis was known to be perfectly horizontal, the telescope could be directed downward at a basin of
31:
450:
The field of the wires could be illuminated; the lamps were placed at some distance from the piers in order not to heat the instrument, and the light passed through holes in the piers and through the hollow axis to the center, whence it was directed to the eye-end by a system of
268:
394:
of the target star by watching the finder circle. The instrument was provided with a clamping apparatus, by which the observer, after having set the approximate declination, could clamp the axis so the telescope could not be moved in declination, except very slowly by a fine
379:
forming a perfectly horizontal mirror and reflecting an image of the crosshairs back up the telescope tube. The crosshairs were adjusted until coincident with their reflection, and the line of sight was then perfectly vertical; in this position the circles were read for the
726:
continued until the end of the century to be employed for determining declinations. The advantages of using a whole circle, it being less liable to change its figure and not requiring reversal in order to observe stars north of the zenith, were then again recognized by
1434:
Julien
Gressot & Daniel Belteki, "Introduction - Re-Assembling the History of Meridian Circles", Daniel Belteki, Julien Gressot, LoĂŻc Jeanson & Jean Davoigneau, "Circles of Precision: Meridian Circles during the Nineteenth and Twentieth Centuries",
747:
431:
being best on account of its slow motion. \ Timings were originally made by an "eye and ear" method, estimating the interval between two beats of a clock. Later, timings were registered by pressing a key, the electrical signal making a mark on a
264:
star, located east or west of the center of the main instrument, and seen through this axis telescope and a small collimating telescope, as the main telescope was rotated, the shape of the pivots, and any wobble of the axis, could be determined.
636:
Once good star catalogs were available a transit telescope could be used anywhere in the world to accurately measure local longitude and time by observing local meridian transit times of catalogue stars. Prior to the invention of the
414:
of a star was to take half of the angular distance between the star observed directly and its reflection observed in a basin of mercury. The average of these two readings was the reading when the line of sight was horizontal, the
359:
and kept as much as possible at the temperature of the outside air, to avoid air currents which would disturb the telescopic view. The building also housed the clocks, recorders, and other equipment for making observations.
210:, Vienna, Austria, built by Repsold & Sons, Hamburg, 1886. Note the counterweights, the short, green cylindrical objects at the outer top of the mechanism, and the four long, thin, microscopes for reading the circles.
443:, a device which allowed matching a vertical crosshair's motion to the star's motion. Set precisely on the moving star, the crosshair would trigger the electrical timing of the meridian crossing, removing the observer's
513:, built by Fauth, 1885. Note the observer's chair between the piers, and the narrow opening in the wall and roof for access to the sky. Because the telescope observes only in the meridian, no rotating dome is necessary.
486:
wire to the horizon. The amount of this inclination was found by taking repeated observations of the zenith distance of a star during the one transit, the pole star being the most suitable because of its slow motion.
691:, but it does not appear to have been much used for right ascension during the 17th century, the method of equal altitudes by portable quadrants or measures of the angular distance between stars with an
193:
only, and is easily accounted for; elsewhere in the sky, refraction causes a complex distortion in coordinates which is more difficult to reduce. Such complex analysis is not conducive to high precision.
570:, instead of a meridian circle, fitted with leveling screws. Extremely sensitive levels are attached to the telescope mount to make angle measurements and the telescope has an eyepiece fitted with a
214:
The state of the art of meridian instruments of the late 19th and early 20th century is described here, giving some idea of the precise methods of construction, operation and adjustment employed.
108:
can function as a transit instrument if its telescope is capable of a full revolution about the horizontal axis. Meridian circles are often called by these names, although they are less specific.
306:
111:
For many years, transit timings were the most accurate method of measuring the positions of heavenly bodies, and meridian instruments were relied upon to perform this painstaking work. Before
1442:
Julien
Gressot & Romain Jeanneret, « Determining the right time, or the establishment of a culture of astronomical precision at Neuchâtel Observatory in the mid-19th century »,
715:
instrument for measuring vertical and horizontal angles, and in 1704, he combined a vertical circle with his transit instrument, so as to determine both co-ordinates at the same time.
861:
camera. As the sky drifts across the field of view, the image built up in the CCD is clocked across (and out of) the chip at the same rate. This allows some improvements:
854:
846:
544:
In practice, none of these adjustments were perfect. The small errors introduced by the imperfections were mathematically corrected during the analysis of the data.
872:
The data can be collected for as long as the telescope is in operation – an entire night is possible, allowing a strip of sky many degrees in length to be scanned.
1555:
Photograph of
Repsold meridian circle at the Lick Observatory from the Lick Observatory Records Digital Archive, UC Santa Cruz Library's Digital Collections
1404:
1238:
1508:
1311:
879:, with an accurately-known position. This eliminates the need for some of the painstaking adjustment of the meridian instrument, although monitoring of
1325:
Stone, Ronald C.; Monet, David G. (1990). "The USNO (Flagstaff
Station) CCD Transit Telescope and Star Positions Measured From Extragalactic Sources".
326:
The telescope consisted of two tubes screwed to the central cube of the axis. The tubes were usually conical and as stiff as possible to help prevent
1395:
778:(a meridian transit circle). Troughton afterwards abandoned the idea and designed the mural circle to take the place of the mural quadrant.
822:
524:, designed to rest on the pivots of the axis, performed this function. By adjusting one of the V-shaped bearings, the bubble was centered.
875:
Data can be compared directly to any reference object which happens to be within the scan – usually a bright extragalactic object, like a
853:
A modern-day example of this type of telescope is the 8 inch (~0.2m) Flagstaff
Astrometric Scanning Transit Telescope (FASTT) at the
953:
929:
1498:
1286:
718:
This latter idea was, however, not adopted elsewhere, although the transit instrument soon came into universal use (the first one at
1270:
707:
The transit instrument consists of a horizontal axis in the direction east and west resting on firmly fixed supports, and having a
494:
lines, and the vertical wires were photographed on the plate by throwing light through the objective lens for one or two seconds.
506:
427:
question. These known intervals were predetermined by timing a star of known declination passing from one wire to the other, the
104:
is likewise mounted on a horizontal axis, but the axis need not be fixed in the east–west direction. For instance, a surveyor's
787:
189:, which tends to make objects appear slightly higher in the sky than they actually are. At the meridian, this distortion is in
711:
fixed at right angles to it, revolving freely in the plane of the meridian. At the same time Rømer invented the altitude and
347:
and objective lens could be interchanged, and the average of the two observations of the same star was free from this error.
311:
1488:
1554:
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1358:
947:
411:
400:
171:
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167:
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34:
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829:
of
Ipswich. The Greenwich instrument had optical and instrumental work by Troughton and Simms to the design of
667:
275:
Near each end of the axis, attached to the axis and turning with it, was a circle or wheel for measuring the
174:
aligns naturally with the meridian at all times. Revolving the telescope about its axis moves it directly in
1420:
966:
609:
Meridian circles have been used since the 18th century to accurately measure positions of stars in order to
288:
226:
was not placed in the middle of the axis, but nearer to one end, to prevent the axis from bending under the
502:
202:
1391:
898:
751:
692:
482:
396:
230:
of the telescope. Later, it was usually placed in the centre of the axis, which consisted of one piece of
186:
1219:
921:
866:
858:
588:
128:
458:
To determine absolute declinations or polar distances, it was necessary to determine the observatory's
247:
1334:
807:
803:
783:
614:
243:
152:
120:
66:
50:
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deduced from observations. The flexure in the horizontal position of the tube was determined by two
1644:
1639:
1623:
1457:
830:
811:
763:
732:
571:
510:
439:
338:—telescopes placed horizontally in the meridian, north and south of the transit circle, with their
296:
207:
1611:
1599:
1540:
771:
613:
them. This is done by measuring the instant when the star passes through the local meridian. Its
490:
339:
330:. The connection to the axis was also as firm as possible, as flexure of the tube would affect
1474:
Meridian Circle
Observations Made at the Lick Observatory, University of California, 1901–1906
1424:
1305:
1266:
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The CCD can collect light for as long as the image is crossing it, allowing a dimmer limiting
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475:
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82:
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with turned cylindrical steel pivots at each end. Several instruments were made entirely of
163:
30:
267:
1362:
799:
684:
626:
592:
179:
371:, the eye end of the telescope had a number of vertical and one or two horizontal wires (
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1228:
892:
723:
610:
463:
452:
433:
368:
74:
1633:
1399:
1386:
1233:
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728:
520:
The rotation axis of the main telescope needed to be exactly horizontal. A sensitive
315:
284:
255:
86:
841:
287:, on a slip of silver set into the face of the circle near the circumference. These
155:
has advantages in the high-precision work for which these instruments are employed:
1587:
1254:
638:
521:
260:
159:
The very simple mounting is easier to manufacture and maintain to a high precision.
147:
Meridian circle at Saint
Petersburg Kunstkamera, built by T.L. Ertel, Germany, 1828
112:
70:
791:
746:
696:
672:
143:
85:. Meridian telescopes rely on the rotation of the sky to bring objects into their
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1086:
1024:
1007:
987:
857:. Modern meridian circles are usually automated. The observer is replaced with a
403:
of the star. The difference between this measurement and the nadir point was the
902:
880:
767:
688:
630:
603:
407:
of the star. A movable horizontal wire or declination-micrometer was also used.
391:
331:
280:
190:
175:
132:
116:
54:
1539:
375:). In observing stars, the telescope was first directed downward at a basin of
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735:
595:
459:
335:
292:
105:
17:
1523:
1510:
1408:. Vol. 27 (11th ed.). Cambridge University Press. pp. 181–183.
1242:. Vol. 11 (11th ed.). Cambridge University Press. pp. 607–615.
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62:
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Attempts were made to record the transits of a star photographically. A
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884:
712:
599:
436:. Later still, the eye end of the telescope was usually fitted with an
327:
319:
845:
The Ron Stone/Flagstaff Astrometric Scanning Transit Telescope of the
242:, which was much more rigid than brass. The pivots rested on V-shaped
876:
563:
467:
227:
78:
695:
being preferred. These methods were very inconvenient, and in 1690,
279:
of the telescope to the zenith or horizon. Generally of 1 to 3
81:, the south point of the horizon, the south celestial pole, and the
1582:
731:, who also improved the method of reading off angles by means of a
683:
A meridian circle enabled the observer to simultaneously determine
57:, while at the same time measuring their angular distance from the
1385:
This article incorporates text from a publication now in the
745:
666:
517:
Meridian circles required precise adjustment to do accurate work.
501:
423:
between the telescope and the basin of mercury was accounted for.
382:
305:
276:
266:
251:
239:
231:
201:
142:
124:
58:
29:
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for extreme precision measurement of star positions. They use an
46:
1227:
914:
762:, who constructed the first modern transit circle in 1806 for
470:, by observing the upper and lower culmination of a number of
617:
above the horizon is noted as well. Knowing one's geographic
1169:
1167:
1091:. Press of John Wilson and Son, Cambridge, Mass. p. 25.
271:
Top view of a circle-reading microscope; from Norton (1867).
1085:
Bond, William C.; Bond, George P.; Winlock, Joseph (1876).
591:) fixed in the plane of the meridian occurred even to the
27:
Astronomical instrument for timing of the passage of stars
1088:
Annals of the Astronomical Observatory of Harvard College
758:
The making of circles was shortly afterwards taken up by
170:
can be indexed directly with such a simple mounting; the
162:
At most locations on the Earth, the meridian is the only
1193:
1191:
1136:
1134:
1132:
1130:
1128:
185:
All objects in the sky are subject to the distortion of
89:
and are mounted on a fixed, horizontal, east–west axis.
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1066:
1064:
1062:
1060:
1058:
1056:
1054:
558:
Some telescopes designed to measure star transits are
1559:
390:
The telescope was next brought up to the approximate
1039:
Chauvenet (1868), p. 132, art. 119; p. 283, art. 195
641:
this was the most reliable source of accurate time.
625:
these measurements can be used to derive the star's
782:them from the years 1818–1819, when two circles by
901:can be accounted for automatically, by monitoring
123:, the measuring of positions (and the deriving of
73:through the north point of the horizon, the north
1477:. W.W. Shannon, superintendent of state printing.
847:United States Naval Observatory Flagstaff Station
1012:. MacMillan Co., New York. p. 317ff, 331ff.
178:, and objects move through its field of view in
1029:. John Wiley & Son, New York. p. 24ff.
1026:A Treatise on Astronomy, Spherical and Physical
995:. Trubner & Co., London. pp. 131, 282.
989:A Manual of Spherical and Practical Astronomy,
1499:U.S. Naval Observatory Flagstaff – 0.2-m FASTT
283:or more in diameter, it was divided to 2 or 5
45:is an instrument for timing of the passage of
602:, but it was not carried into practice until
562:designed to point straight up at or near the
65:mounted so as to allow pointing only in the
8:
950:(Carlsberg Automatic Meridian Circle) (1984)
1466:. Longmans, Green and Company. p. 92.
1452:https://doi.org/10.1177/00218286211068572
891:is still performed with CCD scanners and
410:Another method of observing the apparent
849:, built by Farrand Optical Company, 1981
840:
1566:
978:
928:The first automated instrument was the
671:The world's first meridian circle from
606:constructed a large meridian quadrant.
419:of the circle. The small difference in
151:Fixing a telescope to move only in the
1310:: CS1 maint: archived copy as title (
1303:
1197:
1173:
1140:
1119:
1072:
7:
1489:Description of Airy's Transit Circle
1444:Journal for the History of Astronomy
1327:Proceedings of IAU Symposium No. 141
1161:Bond, Bond and Winlock (1876), p. 26
1152:Bond, Bond and Winlock (1876), p. 25
1110:Bond, Bond and Winlock (1876), p. 27
1101:Bond, Bond and Winlock (1876), p. 25
823:Royal Observatory, Cape of Good Hope
1009:A Compendium of Spherical Astronomy
954:Tokyo Photoelectric Meridian Circle
930:Carlsberg Automatic Meridian Circle
1185:Chauvenet (1868), p. 138, art. 121
855:USNO Flagstaff Station Observatory
754:, built by Warner and Swasey, 1898
587:The idea of having an instrument (
25:
750:The 6-inch transit circle of the
699:invented the transit instrument.
509:'s meridian transit telescope in
507:Chabot Space & Science Center
1617:
1605:
1593:
1581:
1569:
1504:The Carlsberg Meridian Telescope
1378:
1356:The Carlsberg Meridian Telescope
817:The Airy Transit Circles at the
722:being mounted in 1721), and the
788:Georg Friedrich von Reichenbach
1471:Richard Hawley Tucker (1907).
312:Quito Astronomical Observatory
1:
932:, which came online in 1984.
536:lower meridian transits of a
948:Carlsberg Meridian Telescope
794:, and one by Reichenbach at
172:equatorial coordinate system
61:. These are special purpose
1023:Norton, William A. (1867).
986:Chauvenet, William (1868).
819:Royal Greenwich Observatory
1661:
1547:Collier's New Encyclopedia
1263:Princeton University Press
942:Groombridge Transit Circle
776:Groombridge Transit Circle
551:
35:Groombridge transit circle
1524:48.2125194°N 16.2913944°E
1224:Helmert, Friedrich Robert
481:In observations of stars
677:Observatorium Tusculanum
131:) was the major work of
119:, and the perfection of
1541:"Meridian Circle"
1494:Gautier Meridian Circle
1458:Sir Robert Stawell Ball
1405:Encyclopædia Britannica
1392:Dreyer, John Louis Emil
1239:Encyclopædia Britannica
1006:Newcomb, Simon (1906).
967:List of telescope types
837:20th century and beyond
821:(1851) and that at the
351:removable silk covers.
310:Meridian circle at the
254:supported by the pier,
206:Meridian circle at the
1529:48.2125194; 16.2913944
1437:Cahiers François Viète
1430:. Biddle. p. 352.
1220:Clarke, Alexander Ross
1209:Norton (1867), p. 33ff
1048:Norton (1867), p. 39ff
899:Atmospheric refraction
850:
755:
752:U.S. Naval Observatory
680:
514:
447:from the measurement.
323:
272:
211:
187:atmospheric refraction
148:
129:astronomical constants
53:, an event known as a
38:
1463:Elements of Astronomy
924:and analyzed at will.
893:laser interferometers
844:
810:had large circles by
749:
670:
505:
462:, or distance of the
309:
270:
222:The earliest transit
205:
168:celestial coordinates
146:
121:reflecting telescopes
33:
825:(1855) were made by
808:Edinburgh University
804:Cambridge University
784:Johann Georg Repsold
738:as described below.
693:astronomical sextant
598:and is mentioned by
1520: /
1339:1990IAUS..141..369S
1253:Ptolemy, Claudius;
1176:, pp. 182–183.
1122:, pp. 181–182.
831:George Biddell Airy
812:Troughton and Simms
511:Oakland, California
299:screw, which moved
250:, suspended from a
208:Kuffner observatory
1450:(1), 2022, 27–48,
1361:2010-05-28 at the
1259:Ptolemy's Almagest
851:
756:
681:
515:
491:photographic plate
324:
273:
212:
149:
94:transit instrument
39:
560:zenith telescopes
548:Zenith telescopes
472:circumpolar stars
445:personal equation
102:transit telescope
49:across the local
16:(Redirected from
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1299:
1298:
1289:. Archived from
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1277:
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1040:
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1031:
1030:
1020:
1014:
1013:
1003:
997:
996:
983:
827:Ransomes and May
790:were mounted at
760:Edward Troughton
568:altazimuth mount
554:Zenith telescope
538:circumpolar star
417:horizontal point
340:objective lenses
248:friction rollers
198:Basic instrument
21:
1660:
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1439:, III-14, 5-20.
1419:
1416:
1414:Further reading
1390:
1379:
1377:
1369:
1368:
1363:Wayback Machine
1354:
1350:
1324:
1323:
1319:
1302:
1296:
1294:
1287:"Archived copy"
1285:
1284:
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1247:
1229:"Geodesy"
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985:
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975:
963:
938:
917:electronically.
839:
800:Harvard College
744:
705:
685:right ascension
665:
647:
627:right ascension
585:
580:
556:
550:
500:
365:
355:lowered again.
256:counterbalanced
220:
200:
180:right ascension
141:
43:meridian circle
28:
23:
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15:
12:
11:
5:
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1484:
1483:External links
1481:
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1415:
1412:
1411:
1410:
1400:Chisholm, Hugh
1396:Transit Circle
1367:
1366:
1348:
1317:
1278:
1271:
1265:. p. 61.
1245:
1234:Chisholm, Hugh
1211:
1202:
1200:, p. 183.
1187:
1178:
1163:
1154:
1145:
1143:, p. 182.
1124:
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870:
869:to be reached.
838:
835:
743:
740:
724:mural quadrant
704:
701:
664:
661:
646:
643:
584:
581:
579:
576:
552:Main article:
549:
546:
499:
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464:celestial pole
434:strip recorder
405:nadir distance
364:
361:
219:
216:
199:
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98:transit circle
75:celestial pole
26:
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18:Transit circle
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1515:16°17′29.02″E
1512:48°12′45.07″N
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1387:public domain
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1307:
1293:on 2008-11-01
1292:
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1272:0-691-00260-6
1268:
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1255:Toomer, G. J.
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291:were read by
290:
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138:
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133:observatories
130:
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87:field of view
84:
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48:
44:
36:
32:
19:
1624:Solar System
1545:
1473:
1462:
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1436:
1425:
1403:
1372:Attribution:
1371:
1370:
1351:
1345:SAO/NASA ADS
1330:
1326:
1320:
1295:. Retrieved
1291:the original
1281:
1258:
1248:
1237:
1214:
1205:
1181:
1157:
1148:
1115:
1106:
1097:
1087:
1080:
1044:
1035:
1025:
1018:
1008:
1001:
990:
988:
981:
927:
920:Data can be
852:
816:
780:
757:
742:19th century
717:
706:
703:18th century
682:
663:17th century
650:
648:
639:atomic clock
635:
608:
586:
557:
543:
534:
526:
522:spirit level
519:
516:
488:
480:
457:
449:
437:
425:
416:
409:
404:
389:
381:
366:
357:
353:
349:
332:declinations
325:
318:& Sons,
274:
261:spirit level
221:
218:Construction
213:
150:
113:spectroscopy
110:
101:
97:
93:
92:The similar
91:
71:great circle
42:
40:
1612:Outer space
1600:Spaceflight
1527: /
1421:Thomas Dick
1333:: 369–370.
1198:Dreyer 1911
1174:Dreyer 1911
1141:Dreyer 1911
1120:Dreyer 1911
1073:Dreyer 1911
903:temperature
881:declination
768:observatory
764:Groombridge
689:declination
631:declination
604:Tycho Brahe
596:astronomers
438:impersonal
392:declination
369:focal plane
336:collimators
314:. Built by
293:microscopes
289:graduations
191:declination
176:declination
117:photography
55:culmination
1645:Telescopes
1640:Astrometry
1634:Categories
1297:2010-08-27
973:References
796:Königsberg
772:Blackheath
736:microscope
733:micrometer
679:in Denmark
572:micrometer
498:Adjustment
483:refraction
460:colatitude
440:micrometer
373:crosshairs
301:crosshairs
297:micrometer
285:arcminutes
139:Importance
106:theodolite
63:telescopes
1576:Astronomy
1427:Astronomy
1394:(1911). "
911:dew point
867:magnitude
792:Göttingen
720:Greenwich
709:telescope
697:Ole Rømer
673:Ole Rømer
645:Antiquity
623:longitude
466:from the
429:pole star
363:Operation
236:gun metal
224:telescope
166:in which
1460:(1886).
1423:(1848).
1359:Archived
1306:cite web
1257:(1998).
1226:(1911).
961:See also
936:Examples
907:pressure
657:ecliptic
652:Almagest
619:latitude
615:altitude
589:quadrant
583:Overview
421:latitude
412:altitude
401:altitude
345:eyepiece
244:bearings
153:meridian
67:meridian
51:meridian
1562:Portals
1550:. 1921.
1402:(ed.).
1389::
1335:Bibcode
1236:(ed.).
913:of the
885:azimuth
713:azimuth
649:In the
611:catalog
600:Ptolemy
593:ancient
578:History
530:mercury
476:mercury
377:mercury
367:At the
328:flexure
322:, 1889.
320:Hamburg
316:Repsold
37:of 1806
1398:". In
1383:
1269:
956:(1985)
944:(1806)
922:stored
909:, and
887:, and
877:quasar
774:, the
564:zenith
468:zenith
453:prisms
228:weight
125:orbits
79:zenith
77:, the
69:, the
1588:Stars
1343:, at
1232:. In
889:level
397:screw
385:point
383:nadir
277:angle
252:lever
240:steel
232:brass
164:plane
100:, or
83:nadir
59:nadir
47:stars
1312:link
1267:ISBN
806:and
786:and
687:and
629:and
621:and
281:feet
127:and
41:The
1331:141
915:air
859:CCD
770:at
766:'s
675:'s
234:or
1636::
1544:.
1448:53
1446:,
1329:.
1308:}}
1304:{{
1261:.
1222:;
1190:^
1166:^
1127:^
1053:^
991:II
905:,
883:,
833:.
814:.
802:,
659:.
633:.
574:.
455:.
387:.
135:.
115:,
96:,
1564::
1341:.
1337::
1314:)
1300:.
1275:.
895:.
182:.
20:)
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