Journal articles: 'Celestial orientation'

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Zolotareva, A. D., and N. S. Chernetsov. "Celestial Orientation in Birds." Biology Bulletin 48, no. 9 (December 2021): 1503–12. http://dx.doi.org/10.1134/s1062359021090259.

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UGOLINI, A., and S. FELICIONI. "Celestial orientation in Gryllotalpa gryllotalpa." Physiological Entomology 16, no. 3 (September 1991): 355–60. http://dx.doi.org/10.1111/j.1365-3032.1991.tb00573.x.

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Wiltschko, W., and R. Wiltschko. "Magnetic orientation and celestial cues in migratory orientation." Experientia 46, no. 4 (April 1990): 342–52. http://dx.doi.org/10.1007/bf01952167.

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Hakim, Lukmanul, and Yudhiakto Pramudya. "Pengukuran Ketepatan Alignment Sistem Penjejak Gerak Benda Langit dengan Metode Drift Berbantuan Tracker." JIPFRI (Jurnal Inovasi Pendidikan Fisika dan Riset Ilmiah) 4, no. 2 (November 28, 2020): 72–76. http://dx.doi.org/10.30599/jipfri.v4i2.767.

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The simulation of the drift method application using a celestial body tracker has been done. Experiments were carried out by recording the movement of a celestial body tracker with variation orientation of polar angle and azimuth from the true south and polar angle a particular location. The variation is between -2° to +2°. It was found that the greater the difference in the mounting orientation from the true orientation, the greater the shift in altitude and azimuth of the celestial object’s path.

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el Jundi, Basil, Eric J. Warrant, Marcus J. Byrne, Lana Khaldy, Emily Baird, Jochen Smolka, and Marie Dacke. "Neural coding underlying the cue preference for celestial orientation." Proceedings of the National Academy of Sciences 112, no. 36 (August 24, 2015): 11395–400. http://dx.doi.org/10.1073/pnas.1501272112.

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Diurnal and nocturnal African dung beetles use celestial cues, such as the sun, the moon, and the polarization pattern, to roll dung balls along straight paths across the savanna. Although nocturnal beetles move in the same manner through the same environment as their diurnal relatives, they do so when light conditions are at least 1 million-fold dimmer. Here, we show, for the first time to our knowledge, that the celestial cue preference differs between nocturnal and diurnal beetles in a manner that reflects their contrasting visual ecologies. We also demonstrate how these cue preferences are reflected in the activity of compass neurons in the brain. At night, polarized skylight is the dominant orientation cue for nocturnal beetles. However, if we coerce them to roll during the day, they instead use a celestial body (the sun) as their primary orientation cue. Diurnal beetles, however, persist in using a celestial body for their compass, day or night. Compass neurons in the central complex of diurnal beetles are tuned only to the sun, whereas the same neurons in the nocturnal species switch exclusively to polarized light at lunar light intensities. Thus, these neurons encode the preferences for particular celestial cues and alter their weighting according to ambient light conditions. This flexible encoding of celestial cue preferences relative to the prevailing visual scenery provides a simple, yet effective, mechanism for enabling visual orientation at any light intensity.

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Arias, E. F., J. F. Lestrade, and M. Feissel. "Relative orientation of VLBI celestial reference frames." Symposium - International Astronomical Union 128 (1988): 61–66. http://dx.doi.org/10.1017/s0074180900119278.

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Several series of celestial reference frames have been produced during the past few years as part of VLBI geodynamic programs. They consist in coordinates of 20 to 150 extragalactic radio sources with a precision at the level of 0.001″. The relative orientations of these frames and the evolution of each series of catalogs are studied.

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Palavalli-Nettimi, R., and A. Narendra. "Does size affect orientation using celestial cues?" Insectes Sociaux 65, no. 4 (June 26, 2018): 657–62. http://dx.doi.org/10.1007/s00040-018-0640-9.

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el Jundi, Basil, James J. Foster, Lana Khaldy, Marcus J. Byrne, Marie Dacke, and Emily Baird. "A Snapshot-Based Mechanism for Celestial Orientation." Current Biology 26, no. 11 (June 2016): 1456–62. http://dx.doi.org/10.1016/j.cub.2016.03.030.

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Wiltschko, Wolfgang, and Roswitha Wiltschko. "Magnetic versus celestial orientation in migrating birds." Trends in Ecology & Evolution 3, no. 1 (January 1988): 13–15. http://dx.doi.org/10.1016/0169-5347(88)90076-6.

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Dacke, M., Basil el Jundi, Jochen Smolka, Marcus Byrne, and Emily Baird. "The role of the sun in the celestial compass of dung beetles." Philosophical Transactions of the Royal Society B: Biological Sciences 369, no. 1636 (February 19, 2014): 20130036. http://dx.doi.org/10.1098/rstb.2013.0036.

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Recent research has focused on the different types of compass cues available to ball-rolling beetles for orientation, but little is known about the relative precision of each of these cues and how they interact. In this study, we find that the absolute orientation error of the celestial compass of the day-active dung beetle Scarabaeus lamarcki doubles from 16° at solar elevations below 60° to an error of 29° at solar elevations above 75°. As ball-rolling dung beetles rely solely on celestial compass cues for their orientation, these insects experience a large decrease in orientation precision towards the middle of the day. We also find that in the compass system of dung beetles, the solar cues and the skylight cues are used together and share the control of orientation behaviour. Finally, we demonstrate that the relative influence of the azimuthal position of the sun for straight-line orientation decreases as the sun draws closer to the horizon. In conclusion, ball-rolling dung beetles possess a dynamic celestial compass system in which the orientation precision and the relative influence of the solar compass cues change over the course of the day.

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Sandberg, R., and J. Pettersson. "Magnetic orientation of snow buntings (Plectrophenax nivalis), a species breeding in the high Arctic: passage migration through temperate-zone areas." Journal of Experimental Biology 199, no. 9 (September 1, 1996): 1899–905. http://dx.doi.org/10.1242/jeb.199.9.1899.

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Orientation tests were conducted with snow buntings (Plectrophenax nivalis) exposed to artificially manipulated magnetic fields, during both spring and autumn migration. Experiments were run under clear sunset skies and under simulated complete overcast. The birds closely followed experimental shifts of the magnetic fields during both seasons regardless of whether they had access to celestial cues. Clear-sky tests in vertical magnetic fields resulted in a significant bimodal orientation, the directionality of which was almost identical during spring and autumn. When the snow buntings were deprived of celestial directional information and tested in vertical magnetic fields, they failed to show any statistically significant mean directions in either spring or autumn. The results demonstrate that snow buntings possess a magnetic compass and suggest that magnetic cues are of primary importance for their migratory orientation while on passage through temperate-zone areas. However, the axial orientation in vertical magnetic fields under clear skies may indicate an involvement of celestial cues as an auxiliary source of directional information.

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Maoret, Francesco, Giulia Beltrami, Cristiano Bertolucci, and Augusto Foà. "Celestial Orientation with the Sun Not in View." Journal of Biological Rhythms 29, no. 2 (March 28, 2014): 144–47. http://dx.doi.org/10.1177/0748730414525741.

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Diego-Rasilla, Javier, and Rosa Luengo. "Celestial orientation in the marbled newt ( Triturus marmoratus )." Journal of Ethology 20, no. 2 (September 1, 2002): 137–41. http://dx.doi.org/10.1007/s10164-002-0066-7.

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Mathews, P. M., and T. A. Herring. "On the Reference Pole for Earth Orientation and UT1." International Astronomical Union Colloquium 180 (March 2000): 164–70. http://dx.doi.org/10.1017/s0252921100000257.

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AbstractWe show how the study of variations in orientation of a terrestrial reference system (TRS) in space may be done directly in terms of the motion of the pole of the TRS and rotation around it, and how a separation of these variations into low frequency and high frequency (retrograde and prograde diurnal, semidiurnal, · · · ) bands enables one to characterize and model variations belonging to the various bands and to estimate them simultaneously from observational data by a uniform procedure. Introduction of the Celestial Ephemeris Pole (CEP) or other Celestial Intermediate Pole (IP) is not only unnecessary, but also gives rise to needless debate as to whether variations due to particular causes are to be included in the celestial motion of the IP or in its terrestrial motion, and leaves the question of estimation of high-frequency signals in either frame unresolved. In regard to UT1, we point out that the “correction terms” through which the concept of the nonrotating origin is implemented emerge naturally from fundamental kinematical relations, and use this observation to identify the correction terms to be employed when the Earth orientation parameters are defined in relation to the pole of the TRS rather than an IP.

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Capitaine, N. "Definition and realization of the celestial intermediate reference system." Proceedings of the International Astronomical Union 3, S248 (October 2007): 367–73. http://dx.doi.org/10.1017/s1743921308019583.

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AbstractThe transformation between the International Terrestrial Reference System (ITRS) and the Geocentric Celestial Reference system (GCRS) is an essential part of the models to be used when dealing with Earth's rotation or when computing directions of celestial objects in various systems. The 2000 and 2006 IAU resolutions on reference systems have modified the way the Earth orientation is expressed and adopted high accuracy models for expressing the relevant quantities for the transformation from terrestrial to celestial systems. First, the IAU 2000 Resolutions have refined the definition of the astronomical reference systems and transformations between them and adopted the IAU 2000 precession-nutation. Then, the IAU 2006 Resolutions have adopted a new precession model that is consistent with dynamical theories and have addressed definition, terminology or orientation issues relative to reference systems and time scales that needed to be specified after the adoption of the IAU 2000 resolutions. These in particular provide a refined definition of the pole (the Celestial intermediate pole, CIP) and the origin (the Celestial intermediate origin, CIO) on the CIP equator as well as a rigorous definition of sidereal rotation of the Earth. These also allow an accurate realization of the celestial intermediate system linked to the CIP and the CIO that replaces the classical celestial system based on the true equator and equinox of date. This talk explains the changes resulting from the joint IAU 2000/2006 resolutions and reviews the consequences on the concepts, nomenclature, models and conventions in fundamental astronomy that are suitable for modern and future realizations of reference systems. Realization of the celestial intermediate reference system ensuring a micro-arc-second accuracy is detailed.

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Capitaine, Nicole. "Models and nomenclature in Earth rotation." Proceedings of the International Astronomical Union 5, S261 (April 2009): 69–78. http://dx.doi.org/10.1017/s1743921309990172.

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AbstractThe celestial Earth's orientation is required for many applications in fundamental astronomy and geodesy; it is currently determined with sub-milliarcsecond accuracy by astro-geodetic observations. Models for that orientation rely on solutions for the rotation of a rigid Earth model and on the geophysical representation of non-rigid Earth effects. Important IAU 2000/2006 resolutions on reference systems have been passed (and endorsed by the IUGG) that recommend a new paradigm and high accuracy models to be used in the transformation from terrestrial to celestial systems. This paper reviews the consequences of these resolutions on the adopted Earth orientation parameters, IAU precession-nutation models and associated nomenclature. It summarizes the fundamental aspects of the current IAU precession-nutation models and reports on the consideration of General Relativity (GR) in the solutions. This shows that the current definitions and nomenclature for Earth's rotation are compliant with GR and that the IAU precession-nutation is compliant with the IAU 2000 definition of the geocentric celestial reference system in the GR framework; however, the underlying Earth's rotation models basically are Newtonian.

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Grm, Gašper, and Aleksander Grm. "Testing the Functionality and Applicability of Smart Devices for a Handheld Celestial Navigation System." Naše more 68, no. 3 (September 2021): 157–66. http://dx.doi.org/10.17818/nm/2021/3.3.

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In this paper, the functionality and applicability of smart devices for the purpose of handheld celestial navigation systems is investigated. The main instrument used to determine observer position (altitude measurements) in celestial navigation is the sextant. The use of a sextant and almanac or computer is a classical approach to determining the observer's celestial position. This approach has two significant limitations, firstly the time window for the measurements is short, and secondly, the view of the ocean horizon must be clear. With the use of smart devices, we can overcome these two obstacles and create a so-called handheld celestial navigation system. Currently, smart devices have very accurate sensors to measure various physical quantities such as acceleration, angular velocity, orientation, etc. We are particularly interested in validating the orientation sensor for measuring the altitude and azimuth of the celestial body. The altitude of the celestial body is the primary parameter in determining the celestial position using a sextant. The idea is to replace the sextant with a smart device to measure the altitude and possibly the azimuth of the celestial body. To test this idea, two types of experiments are designed. In the first, a system on a tripod to obtain the most accurate measurements possible is set. Such tests will provide detailed information about the accuracy of the smart device's sensors and its applicability in measuring altitude and azimuth. The test system will essentially resemble a theodolite device. In the second experiment, a hands-free measurement experiment that resembles a sextant to test the idea for practical use and functionality in the process of celestial positioning is set. The observed data show that the results of the measurements under controlled conditions are promising and within reasonable bounds for the accuracy of celestial positioning. Estimates of the position error by the graphical method are in the range of 10 Nm to 30 Nm. In order to obtain a fully functional stand-alone celestial positioning system, the proposed assembly needs to be improved through several unchallenging upgrades. A fully functional system can be considered as a cheap off-the-shelf handheld Celestial Navigational System (CNS).

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Ugolini, A., B. Vignali, C. Castellini, and M. Lindström. "Zonal Orientation and Spectral Filtering in Talitrus Saltator (Amphipoda, Talitridae)." Journal of the Marine Biological Association of the United Kingdom 76, no. 2 (May 1996): 377–89. http://dx.doi.org/10.1017/s0025315400030617.

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Adult individuals of Talitrus saltator were tested for celestial orientation in a plexiglass bowl covered with colour filters of different wavelengths. Results show that T. saltator can recognize the sun and use it for orientation only at γ <450 nm. At γ >500 nm, the sight of the sun (and sky) only induces phototactic behaviour. It has also been confirmed that an important celestial orienting factor is perceived in the UV range. Variations in populations from diversely oriented coastlines are discussed. Preliminary results of electroretino-graphic responses indicate the presence of at least two visual pigments in the eye and a steep decrease in sensitivity for γ >500 nm.

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Yang, Peng, Li Xie, and Jilin Liu. "Simultaneous celestial positioning and orientation for the lunar rover." Aerospace Science and Technology 34 (April 2014): 45–54. http://dx.doi.org/10.1016/j.ast.2011.07.003.

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Beugnon, G. "Time-compensated celestial orientation in the cricket Pteronemobius lineolatus." Behavioural Processes 15, no. 1 (August 1987): 109–15. http://dx.doi.org/10.1016/0376-6357(87)90036-2.

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Nguyen, Tu Anh Thi, M. Jerome Beetz, Christine Merlin, and Basil el Jundi. "Sun compass neurons are tuned to migratory orientation in monarch butterflies." Proceedings of the Royal Society B: Biological Sciences 288, no. 1945 (February 24, 2021): 20202988. http://dx.doi.org/10.1098/rspb.2020.2988.

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Every autumn, monarch butterflies migrate from North America to their overwintering sites in Central Mexico. To maintain their southward direction, these butterflies rely on celestial cues as orientation references. The position of the sun combined with additional skylight cues are integrated in the central complex, a region in the butterfly's brain that acts as an internal compass. However, the central complex does not solely guide the butterflies on their migration but also helps monarchs in their non-migratory form manoeuvre on foraging trips through their habitat. By comparing the activity of input neurons of the central complex between migratory and non-migratory butterflies, we investigated how a different lifestyle affects the coding of orientation information in the brain. During recording, we presented the animals with different simulated celestial cues and found that the encoding of the sun was narrower in migratory compared to non-migratory butterflies. This feature might reflect the need of the migratory monarchs to rely on a precise sun compass to keep their direction during their journey. Taken together, our study sheds light on the neural coding of celestial cues and provides insights into how a compass is adapted in migratory animals to successfully steer them to their destination.

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Folkner, W. M., and J. S. Border. "Linking the planetary ephemeris to the International Celestial Reference Frame." Proceedings of the International Astronomical Union 10, H16 (August 2012): 219–20. http://dx.doi.org/10.1017/s1743921314005493.

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AbstractThe largest uncertainty in the ephemerides for the inner planets is in the orientation of the dynamical system to the celestial reference frame. A program of VLBI measurements of spacecraft in orbit about Venus and Mars has been performed to reduce the orientation uncertainty to 0.2 milliarcseconds.

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Tyagi, Tushar, and Sanjay Kumar Bhardwaj. "Orientation cues and mechanisms used during avian navigation: A review." Journal of Applied and Natural Science 13, no. 2 (June 2, 2021): 627–40. http://dx.doi.org/10.31018/jans.v13i2.2684.

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The navigational systems of different animal species are by a wide margin less notable as compared to birds. Humans have been interested in how migratory birds discover their way more than thousands of miles for quite a long time. This review summarizes the cues and compass mechanisms applied in orientation and navigation by non-migrants, diurnal and nocturnal migrants. The magnetic compass, landmarks, olfactory, and memory of spatial cues en route were utilized in homing and migration. The equivalent is valid for the sun compass despite the fact that its job during migration might be undeniably less significant than commonly presumed. Stellar compass and celestial rotation, as a result of their nighttime accessibility, appear to influence the direction of nighttime migrants during the course of migration. The celestial cues go through notable changes because of the latitude shift during bird migration. Sunset cues alter their location with seasons and latitudes. The recognizable stars lose height and lastly vanish underneath the horizon, whereas new stars show up. These new ones must be calibrated. As celestial rotation not imparting a reference, it is not unexpected that the magnetic compass turns into the main cue that controls the directional importance of stars and sunset cues. Field studies have revealed that, in certain species, a considerable extent of individuals get back to similar breeding, overwintering, and stopover areas in progressive years. This review proposes that migratory birds have advanced uncommon cognitive capacities that empower them to achieve these accomplishments.

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McCarthy, Dennis D. "Earth Orientation - The Current and Future Situation." Symposium - International Astronomical Union 166 (1995): 287–91. http://dx.doi.org/10.1017/s0074180900228210.

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Sub-milliarcsecond astrometry often requires an accurate characterization of the orientation of the Earth in a quasi-inertial reference frame. The International Earth Rotation Service (IERS) standards provide the current state of the art in the transformation between celestial and terrestrial reference systems. Improvements in the determination of Earth orientation parameters which describe this transformation continue to be made. Current and future capabilities are given.

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Capitaine, Nicole. "Definition of the Celestial Ephemeris Pole and the Celestial Ephemeris Origin." International Astronomical Union Colloquium 180 (March 2000): 153–63. http://dx.doi.org/10.1017/s0252921100000245.

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AbstractThe adoption of the International Celestial Reference System (ICRS) by the IAU in use since 1 January 1998, and the accuracy achieved by the most recent models and observations of Earth rotation call for a redefinition of the Earth Orientation Parameters (EOP). First, the precession-nutation parameters and Greenwich sidereal time, which are currently defined in the FK5 System, have to be re-defined to be consistent with the ICRS. Second, the current definition of the Celestial Ephemeris Pole (CEP) has to be extended in order to be consistent with the most recent models for nutation and polar motion at a microarsecond accuracy including diurnal and sub-diurnal components, as well as with new strategies of observations. Such issues have been under consideration by the subgroup T5 named “Computational Consequences” of the IAU Working Group “ICRS”. This paper gives, as the basis for future recommendations, the preliminary proposals of the subgroup T5 for a modern definition of the CEP, for the definition of more basic EOP in the ICRS and for the choice of a new origin on the equator of the CEP in place of the equinox. Then, the paper emphasizes the use of the Celestial Ephemeris Origin (CEO) which is defined as the “non-rotating origin” in the celestial frame on the equator of the CEP.

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Mueller, Ivan I. "The First Decade of the IERS." International Astronomical Union Colloquium 178 (2000): 201–13. http://dx.doi.org/10.1017/s0252921100061340.

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AbstractThe International Earth Rotation Service (IERS) was established in 1987 by the International Astronomical Union (IAU) and the International Union of Geodesy and Geophysics (IUGG), and it began operation on 1 January 1988. The primary objectives of the IERS are to serve the astronomical, geodetic and geophysical communities by providing the following: •The International Celestial Reference System (ICRS) and its realization, the International Celestial Reference Frame (ICRF).•The International Terrestrial Reference System (ITRS) and its realization, the International Terrestrial Reference Frame (ITRF).•Earth orientation parameters required to study Earth orientation variations and to transform between the ICRF and the ITRF.•Geophysical data to interpret time/space variations of the ITRF with respect to the ICRF, i.e., of the Earth orientation parameters, and to model such variations.•Standards, constants and models (i.e., conventions) encouraging international adherence.This presentation primarily covers the first three IERS functions from the operational point of view.

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Spasova, Mina, P. Stoeva, and A. Stoev. "Archaeoastronomy in the Big Data Age: Origin and Peculiarities of Obtaining Data on Objects and Artifacts." Proceedings of the International Astronomical Union 15, S367 (December 2019): 455–57. http://dx.doi.org/10.1017/s174392132100017x.

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AbstractThe impressive transition from an era of scientific data scarcity to an era of overproduction has become particularly noticeable in archaeoastronomy. The collection of astronomical information about prehistoric societies allows the accumulation of global data on: – the oldest traces of astronomical activity on Earth, emotional and rational display of celestial phenomena in astronomical folklore, “folk astronomy” and timekeeping, in fine arts and architecture, in everyday life; – the most ancient applied “astronomy” – counting the time by lunar phases, accumulation and storage of ancient databases in drawings and pictographic compositions in caves and artificially constructed objects; – “horizon” astronomy as an initial form of observational cult astronomy, preserved only in characteristic material monuments (the oldest cult observatories) with indisputable astronomical orientations. The report shows the importance of collecting the maximum number of artifacts and monuments from prehistory associated with the early emergence of interest in celestial phenomena. Spiritual, emotional and rational (including practical) needs that have aroused interest in Heaven are discussed. The huge variety of activities in realizing the regularity (cyclicity) of celestial phenomena as a stimulus for their use for orientation in space and time is shown.

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el Jundi, Basil, James J. Foster, Marcus J. Byrne, Emily Baird, and Marie Dacke. "Spectral information as an orientation cue in dung beetles." Biology Letters 11, no. 11 (November 2015): 20150656. http://dx.doi.org/10.1098/rsbl.2015.0656.

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During the day, a non-uniform distribution of long and short wavelength light generates a colour gradient across the sky. This gradient could be used as a compass cue, particularly by animals such as dung beetles that rely primarily on celestial cues for orientation. Here, we tested if dung beetles can use spectral cues for orientation by presenting them with monochromatic (green and UV) light spots in an indoor arena. Beetles kept their original bearing when presented with a single light cue, green or UV, or when presented with both light cues set 180° apart. When either the UV or the green light was turned off after the beetles had set their bearing in the presence of both cues, they were still able to maintain their original bearing to the remaining light. However, if the beetles were presented with two identical green light spots set 180° apart, their ability to maintain their original bearing was impaired. In summary, our data show that ball-rolling beetles could potentially use the celestial chromatic gradient as a reference for orientation.

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WU Liang, 吴量, 王建立 WANG Jian-li, and 王昊京 WANG Hao-jing. "Three FOV celestial positioning and orientation with minimum loss function." Optics and Precision Engineering 23, no. 3 (2015): 904–12. http://dx.doi.org/10.3788/ope.20152303.0904.

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Wiltschko, Roswitha, Ursula Munro, Hugh Ford, and Wolfgang Wiltschko. "Orientation in migratory birds: time-associated relearning of celestial cues." Animal Behaviour 62, no. 2 (August 2001): 245–50. http://dx.doi.org/10.1006/anbe.2001.1751.

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Itul, Tiberiu Pavel, and Doina Liana Pisla. "Kinematic-Dimensional Analysis of Parallel Robot Used for Orientation." Solid State Phenomena 166-167 (September 2010): 229–34. http://dx.doi.org/10.4028/www.scientific.net/ssp.166-167.229.

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In the paper a very simple parallel robot intended for some celestial orientation applications (satellite dishes, sun trackers, cameras, telescopes etc.) is proposed. After describing the mechanism and its kinematics, the workspace and the presence of the singularities are studied. The dimensional optimization to maximize the workspace is described, taking into account the constraints due to telescopic leg lengths and transmission angles.

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Khaldy, Lana, Claudia Tocco, Marcus Byrne, and Marie Dacke. "Compass Cue Integration and Its Relation to the Visual Ecology of Three Tribes of Ball-Rolling Dung Beetles." Insects 12, no. 6 (June 6, 2021): 526. http://dx.doi.org/10.3390/insects12060526.

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To guide their characteristic straight-line orientation away from the dung pile, ball-rolling dung beetles steer according to directional information provided by celestial cues, which, among the most relevant are the sun and polarised skylight. Most studies regarding the use of celestial cues and their influence on the orientation system of the diurnal ball-rolling beetle have been performed on beetles of the tribe Scarabaeini living in open habitats. These beetles steer primarily according to the directional information provided by the sun. In contrast, Sisyphus fasciculatus, a species from a different dung-beetle tribe (the Sisyphini) that lives in habitats with closely spaced trees and tall grass, relies predominantly on directional information from the celestial pattern of polarised light. To investigate the influence of visual ecology on the relative weight of these cues, we studied the orientation strategy of three different tribes of dung beetles (Scarabaeini, Sisyphini and Gymnopleurini) living within the same biome, but in different habitat types. We found that species within a tribe share the same orientation strategy, but that this strategy differs across the tribes; Scarabaeini, living in open habitats, attribute the greatest relative weight to the directional information from the sun; Sisyphini, living in closed habitats, mainly relies on directional information from polarised skylight; and Gymnopleurini, also living in open habitats, appear to weight both cues equally. We conclude that, despite exhibiting different body size, eye size and morphology, dung beetles nevertheless manage to solve the challenge of straight-line orientation by weighting visual cues that are particular to the habitat in which they are found. This system is however dynamic, allowing them to operate equally well even in the absence of the cue given the greatest relative weight by the particular species.

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Vondrák, J., C. Ron, I. Pešek, and A. Čepek. "Earth Orientation Parameters 1899.7-1992.0 In The Hipparcos Reference Frame." Highlights of Astronomy 11, no. 1 (1998): 553. http://dx.doi.org/10.1017/s1539299600022103.

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The optical astrometry observations of latitude/universal time variations made with 48 instruments at 31 observatories are used to determine the Earth orientation parameters (EOP) since the beginning of the century. The Hipparcos Catalogue is used to bring more than four million individual observations, made in the interval 1899.7-1992.0, into the International Celestial Reference System. The Earth orientation parameters (polar motion, celestial pole offsets and, since 1956.0, also universal time UT1) are determined at 5-day intervals, with average uncertainties ranging from 8 mas (in the eighties) to about 40 mas (in the forties). Making use of very long series of ground-based observations, the solution also leads to the improvement of proper motions of about ten per cent of the observed Hipparcos stars, with precision of ±0.2 — 0.5 mas/yr. In addition, 474 auxiliary parameters, describing the rheological properties of the Earth and seasonal deviations of the observations at contributing observatories, are found. The new solution provides the EOP series suitable for further analyses, e.g., for studying long-periodic polar motion, length-of-day changes or precession/nutation.

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Feissel, M. "Permanent Milliarcsecond Link of Celestial and Terrestrial Reference Systems." International Astronomical Union Colloquium 127 (1991): 101–7. http://dx.doi.org/10.1017/s0252921100063624.

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AbstractThe celestial reference system and the terrestial reference system of the International Earth Rotation Service (IERS) are realized on the basis of observation programs in Very Long Baseline radio Interferometry and laser ranging to the Moon and artificial satellites. The celestial frame is materialized by the equatorial coordinates of radio sources observed in VLBI; the terrestrial frame is materialized by the cartesian coordinates of the terrestrial sites monitored by the three techniques. Series of the Earth Orientation Parameters are derived from the same observations. These series provide a permanent link between the celestial system and the terrestrial system at the level of 0.001”.The global adjustment in which the reference systems are defined and realized is described, and the metrological properties of the frames and of the derived EOP are evaluated.

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Massy, Richard, Will L. S. Hawkes, Toby Doyle, Jolyon Troscianko, Myles H. M. Menz, Nicholas W. Roberts, Jason W. Chapman, and Karl R. Wotton. "Hoverflies use a time-compensated sun compass to orientate during autumn migration." Proceedings of the Royal Society B: Biological Sciences 288, no. 1959 (September 22, 2021): 20211805. http://dx.doi.org/10.1098/rspb.2021.1805.

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The sun is the most reliable celestial cue for orientation available to daytime migrants. It is widely assumed that diurnal migratory insects use a ‘time-compensated sun compass’ to adjust for the changing position of the sun throughout the day, as demonstrated in some butterfly species. The mechanisms used by other groups of diurnal insect migrants remain to be elucidated. Migratory species of hoverflies (Diptera: Syrphidae) are one of the most abundant and beneficial groups of diurnal migrants, providing multiple ecosystem services and undergoing directed seasonal movements throughout much of the temperate zone. To identify the hoverfly navigational strategy, a flight simulator was used to measure orientation responses of the hoverflies Scaeva pyrastri and Scaeva selenitica to celestial cues during their autumn migration. Hoverflies oriented southwards when they could see the sun and shifted this orientation westward following a 6 h advance of their circadian clocks. Our results demonstrate the use of a time-compensated sun compass as the primary navigational mechanism, consistent with field observations that hoverfly migration occurs predominately under clear and sunny conditions.

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García Quintela, Marco V., A. César González-García, David Espinosa-Espinosa, Andrea Rodríguez-Antón, and Juan A. Belmonte. "An Archaeology of the Sky in Gaul in the Augustan Period." Journal of Skyscape Archaeology 8, no. 2 (February 13, 2023): 163–207. http://dx.doi.org/10.1558/jsa.21048.

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Ancient Gaul was transformed during the reign of Augustus (r. 31 BC–14 AD) through a major programme of city building. The new Roman cities were constructed according to topographic, health and ritual considerations, and we hypothesise that their orientations also reflect distinct celestial conceptions held by the Gauls and by the Roman emperor Augustus. Our study of the orientation of 60 cities verifies the existence of coherent patterns, and distinguishes two dominant schemes: a pattern prevailing in the south and focused on cardinal orientations, possibly related to the dies natalis of Augustus; and a pattern dominant in the north, focused on the dates of the festivities at the beginning of the seasons from the Celtic tradition. We argue that the orientation of the cities was used by the Gallic elites to express the validity of their cultural tradition when they became a part of the Roman Empire.

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Ugolini, A., F. Morabito, and C. Castellini. "Spectral filtering and celestial orientation in the semi-terrestrial isopodTylos europaeus." Ethology Ecology & Evolution 9, no. 3 (July 1997): 2261–268. http://dx.doi.org/10.1080/08927014.1997.9522886.

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Malkin, Zinovy, Richard Gross, Dennis McCarthy, Aleksander Brzeziński, Nicole Capitaine, Véronique Dehant, Chengli Huang, Harald Schuh, Jan Vondrák, and Yaroslav Yatskiv. "On the eve of the 100th anniversary of IAU Commission 19/A2 “Rotation of the Earth”." Proceedings of the International Astronomical Union 13, S349 (December 2018): 325–31. http://dx.doi.org/10.1017/s1743921319000462.

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AbstractIAU Commission 19 began in 1919 with the birth of the IAU at the Brussels Conference, where Standing Committee 19 on Latitude Variations was established as one of 32 standing committees. At the first IAU General Assembly in 1922, Standing Committee 19 became Commission 19 “Variation of Latitude”. In the beginning, the main topic of the Commission was the investigation of polar motion. Later, its activities included observations and theory of Earth rotation and connections between Earth orientation variations and geophysical phenomena. As a result, in 1964 at the XII IAU General Assembly, the Commission was renamed “Rotation of the Earth”. The investigation of Earth orientation variations is primarily based on observations of natural and artificial celestial objects. Therefore, maintenance of the international terrestrial and celestial reference frames, as well as the coordinate transformation between the frames and the improvement of the model of precession/nutation, have always been among the primary Commission topics. In 1987, the IAU through Commissions 19 and 31 “Time” established, jointly with the International Union of Geodesy and Geophysics, what is now known as the International Earth Rotation and Reference Systems Service. Commission 19 continued to work to develop methods to improve the accuracy and understanding of Earth orientation variations and related reference systems and frames as well as theoretical studies of Earth rotation. In 2015, Commission 19 was renewed as Commission A2 “Rotation of the Earth” continuing Commission 19’s functions and linking the astronomical community to other scientific organizations such as the International Association of Geodesy, International VLBI Service for Geodesy and Astrometry, International GNSS Service, International Laser Ranging Service and International DORIS Service. During its entire history, IAU Commission 19/A2 has always worked in close cooperation with these and other related services to improve the accuracy and consistency of the Earth orientation parameters and celestial and terrestrial reference frames.

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Weindler, P., M. Baumetz, and W. Wiltschko. "The direction of celestial rotation influences the development of stellar orientation in young garden warblers (Sylvia borin)." Journal of Experimental Biology 200, no. 15 (January 1, 1997): 2107–13. http://dx.doi.org/10.1242/jeb.200.15.2107.

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The study presented here was conducted in order to analyze the role of the direction of celestial rotation in the development of stellar orientation in young migratory birds. The test birds were garden warblers, Sylvla borin, which leave their breeding ground on a southwesterly compass course. The birds were hand-raised and, during the premigratory period, exposed to an artificial 'sky' in the local geomagnetic field. For the control group C, the star pattern was rotating in the natural direction, with the centre of rotation and magnetic North coinciding. For the three experimental groups, the star pattern was rotating in the opposite direction; for group E1, the centre of rotation coincided with magnetic North, for group E2 the centre of rotation was at magnetic West and for group E3 it was at magnetic East. During autumn migration, the birds were tested without magnetic information under the same, now stationary, sky. All four groups were able to use stellar information for orientation, but only the control group preferred the normal southwesterly course. The three experimental groups, in contrast, all oriented towards a significantly different direction, preferring due south. The results for group E1 showed less scatter than those for the other two experimental groups. These results indicate that the direction of celestial rotation is crucial for the development of the normal migratory course with respect to the stars in young garden warblers. Establishing the species-specific southwesterly migratory course requires an interaction between celestial rotation and magnetic cues; this interaction appears to depend on the natural direction of celestial rotation. Rotation in the reverse direction allowed the birds to respond only in a manner that oriented them away from the centre of rotation.

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Dacke, M., M. J. Byrne, E. Baird, C. H. Scholtz, and E. J. Warrant. "How dim is dim? Precision of the celestial compass in moonlight and sunlight." Philosophical Transactions of the Royal Society B: Biological Sciences 366, no. 1565 (March 12, 2011): 697–702. http://dx.doi.org/10.1098/rstb.2010.0191.

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Prominent in the sky, but not visible to humans, is a pattern of polarized skylight formed around both the Sun and the Moon. Dung beetles are, at present, the only animal group known to use the much dimmer polarization pattern formed around the Moon as a compass cue for maintaining travel direction. However, the Moon is not visible every night and the intensity of the celestial polarization pattern gradually declines as the Moon wanes. Therefore, for nocturnal orientation on all moonlit nights, the absolute sensitivity of the dung beetle's polarization detector may limit the precision of this behaviour. To test this, we studied the straight-line foraging behaviour of the nocturnal ball-rolling dung beetle Scarabaeus satyrus to establish when the Moon is too dim—and the polarization pattern too weak—to provide a reliable cue for orientation. Our results show that celestial orientation is as accurate during crescent Moon as it is during full Moon. Moreover, this orientation accuracy is equal to that measured for diurnal species that orient under the 100 million times brighter polarization pattern formed around the Sun. This indicates that, in nocturnal species, the sensitivity of the optical polarization compass can be greatly increased without any loss of precision.

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Menzel, Randolf, Lars Chittka, Stefan Eichmüller, Karl Geiger, Dagmar Peitsch, and Peter Knoll. "Dominance of Celestial Cues over Landmarks Disproves Map-Like Orientation in Honey Bees." Zeitschrift für Naturforschung C 45, no. 6 (June 1, 1990): 723–26. http://dx.doi.org/10.1515/znc-1990-0625.

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Abstract A recent model of landmark orientation by the bee assumes that the memory of the landmarks is arranged in a kind of a mental map. Our experiments disprove this assumption and show that the sun compass dominates the orientation without any indication of mental operations within a map-like representation of landmarks or of compass vectors and distances.

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Liu, N., S. B. Lambert, E. F. Arias, J. C. Liu, and Z. Zhu. "Evaluation of the ICRF stability from a position time series analysis." Astronomy & Astrophysics 659 (March 2022): A75. http://dx.doi.org/10.1051/0004-6361/202142632.

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Context. The celestial reference frame is established on the basis of the absolute positions of extragalactic sources that are assumed to be fixed in space. The fixing of the axes is one of the crucial points for the concept behind the International Celestial Reference System (ICRS). However, due to various effects such as its intrinsic activity, the apparent position of the extragalactic sources may vary with time, resulting in a time-dependent deviation of the frame axes that are defined by the positions of these sources. Aims. We aim to evaluate the axis stability of the third realization of the International Celestial Reference Frame (ICRF3). Methods. We first derived the extragalactic source position time series from observations of very long baseline interferometry (VLBI) at the dual S∕X-band (2.3/8.4 GHz) between August 1979 and December 2020. We measured the stability of the ICRF3 axes in terms of the drift and scatter around the mean: (i) we estimated the global spin of the ICRF3 axes based on the apparent proper motion (slope of the position time series) of the defining sources of the ICRF3; (ii) we also constructed the yearly representations of the ICRF3 through annually averaged positions of the defining sources of the ICRF3 and estimated the dispersion in the axes orientation of these yearly frames. Results. The global spin is no higher than 0.8 μas yr-1 for each ICRF3 axis with an uncertainty of 0.3 μas yr-1, corresponding to an accumulated deformation smaller than 30 μas for the celestial frame axes during 1979.6–2021.0. The axes orientation of the yearly celestial frame becomes more stable as time elapses, with a standard deviation of 10 μas–20 μas for each axis. Conclusions. The axes of the ICRF3 are stable at approximately 10 μas–20 μas from 1979.6–2021.0 and the axes stability does not degrade after the adoption of the ICRF3.

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Gross, R. S. "Observations of the Celestial Ephemeris Pole." Highlights of Astronomy 10 (1995): 232–36. http://dx.doi.org/10.1017/s1539299600011084.

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AbstractSpace-geodetic measurement systems are capable of determining: (1) a terrestrial, body-fixed reference frame defined in practice by the stated positions and secular motions of a set of observing stations, (2) a celestial, space-fixed reference frame defined in practice by the stated locations of celestial objects, and (3) the rotation parameters linking these two frames together. Five parameters are conventionally used to specify the orientation of the terrestrial frame with respect to the celestial frame: two nutation parameters, two polar motion parameters, and one spin parameter. The celestial ephemeris pole (CEP) is defined as the north pole of that axis about which the spin parameter (UT1) is measured. The two nutation parameters locate the CEP in the celestial frame, and the two polar motion parameters locate the CEP in the terrestrial frame. By examining the frame transformation matrices, an expression relating the location of the rotation pole to that of the CEP can be derived. In order to compare theoretical predictions with observations, results of models for the effect on the nutations of geophysical excitation processes such as diurnal oceanic current and sea level height variations should not only be given in terms of the location of the CEP (rather than of the rotation pole), but must also account for the resonance effects of the free core nutation.

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Pomozi, István, Gábor Horváth, and Rüdiger Wehner. "How the clear-sky angle of polarization pattern continues underneath clouds: full-sky measurements and implications for animal orientation." Journal of Experimental Biology 204, no. 17 (September 1, 2001): 2933–42. http://dx.doi.org/10.1242/jeb.204.17.2933.

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SUMMARY One of the biologically most important parameters of the cloudy sky is the proportion P of the celestial polarization pattern available for use in animal navigation. We evaluated this parameter by measuring the polarization patterns of clear and cloudy skies using 180° (full-sky) imaging polarimetry in the red (650nm), green (550nm) and blue (450nm) ranges of the spectrum under clear and partly cloudy conditions. The resulting data were compared with the corresponding celestial polarization patterns calculated using the single-scattering Rayleigh model. We show convincingly that the pattern of the angle of polarization (e-vectors) in a clear sky continues underneath clouds if regions of the clouds and parts of the airspace between the clouds and the earth surface (being shady at the position of the observer) are directly lit by the sun. The scattering and polarization of direct sunlight on the cloud particles and in the air columns underneath the clouds result in the same e-vector pattern as that present in clear sky. This phenomenon can be exploited for animal navigation if the degree of polarization is higher than the perceptual threshold of the visual system, because the angle rather than the degree of polarization is the most important optical cue used in the polarization compass. Hence, the clouds reduce the extent of sky polarization pattern that is useful for animal orientation much less than has hitherto been assumed. We further demonstrate quantitatively that the shorter the wavelength, the greater the proportion of celestial polarization that can be used by animals under cloudy-sky conditions. As has already been suggested by others, this phenomenon may solve the ultraviolet paradox of polarization vision in insects such as hymenopterans and dipterans. The present study extends previous findings by using the technique of 180° imaging polarimetry to measure and analyse celestial polarization patterns.

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Card, Ashley, Caitlin McDermott, and Ajay Narendra. "Multiple orientation cues in an Australian trunk-trail-forming ant, Iridomyrmex purpureus." Australian Journal of Zoology 64, no. 3 (2016): 227. http://dx.doi.org/10.1071/zo16046.

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Ants use multiple cues for navigating to a food source or nest location. Directional information is derived from pheromone trails or visual landmarks or celestial objects. Some ants use the celestial compass information along with an ‘odometer’ to determine the shortest distance home, a strategy known as path integration. Some trail-following ants utilise visual landmark information whereas few of the solitary-foraging ants rely on both path integration and visual landmark information. However, it is unknown to what degree trail-following ants use path integration and we investigated this in a trunk-trail-following ant, Iridomyrmex purpureus. Trunk-trail ants connect their nests to food sites with pheromone trails that contain long-lasting orientation information. We determined the use of visual landmarks and the ability to path integrate in a trunk-trail forming ant. We found that experienced animals switch to relying on visual landmark information, and naïve individuals rely on odour trails. Ants displaced to unfamiliar locations relied on path integration, but, surprisingly, they did not travel the entire homebound distance. We found that as the homebound distance increased, the distance ants travelled relying on the path integrator reduced.

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Wiltschko, W., and R. Wiltschko. "Magnetic orientation in birds." Journal of Experimental Biology 199, no. 1 (January 1, 1996): 29–38. http://dx.doi.org/10.1242/jeb.199.1.29.

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The magnetic field of the earth is an omnipresent, reliable source of orientational information. A magnetic compass has been demonstrated in 18 species of migrating birds. In all species studied with regard to its functional properties, it was found to be an 'inclination compass', i.e. the birds derive directional information from the inclination of the field lines, and thus distinguish between 'poleward' and 'equatorward' rather than 'north' and 'south'. Such a mechanism means that birds from the northern and southern hemisphere may rely on the same migratory programme. Long-distance migrants, however, face the problem that their magnetic compass gives bimodal information at the magnetic equator. Transfers of information between the magnetic field and celestial sources of directional information have been demonstrated; the two systems interact in a complex way. The data on the use of magnetic parameters for position finding are less clear. The experiments involve releases of homing pigeons; correlations of their orientation with natural variations in the magnetic field and the effects of magnetic manipulation reveal an enormous variability. The role of magnetic parameters in the multifactorial navigational system is poorly understood.

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Wiltschko, Wolfgang, Peter Weindler, and Roswitha Wiltschko. "Interaction of Magnetic and Celestial Cues in the Migratory Orientation of Passerines." Journal of Avian Biology 29, no. 4 (December 1998): 606. http://dx.doi.org/10.2307/3677181.

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Gebgart, A. Ya, and M. P. Kolosov. "Design features of the lens objectives of celestial-orientation apparatus for spacecraft." Journal of Optical Technology 82, no. 6 (June 1, 2015): 357. http://dx.doi.org/10.1364/jot.82.000357.

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Vondrák, J., C. Ron, and I. Pešek. "Earth Rotation in the Hipparcos Reference Frame." International Astronomical Union Colloquium 165 (1997): 115–22. http://dx.doi.org/10.1017/s0252921100046431.

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AbstractNew determination of the Earth orientation parameters (EOP), based on optical astrometry observations since the beginning of the century, is now under preparation by the Working group established by Commission 19 of the IAU. The Hipparcos catalog is to define the celestial reference frame in which the new series of EOP are to be described. The novelties of the prepared solution are the higher resolution (5 days) and more parameters estimated from the solution (celestial pole offsets, rheological parameters of the Earth, certain instrumental constants). The mathematical model of the solution is described, and the results based on the observations made with 46 instruments at 29 observatories and a preliminary Hipparcos catalog are presented.

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Boucher, C., and Z. Altamimi. "A Terrestrial Reference System Consistent with WGRS." International Astronomical Union Colloquium 127 (1991): 211–14. http://dx.doi.org/10.1017/s025292110006379x.

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AbstractThe IAU and IUGG has jointly established in 1988 an International Earth Rotation Service (IERS) which is in charge of the realization of conventional celestial and terrestrial reference systems, together with the determination of earth orientation parameters which connect them.The theoretical definition of the terrestrial reference system which is realized by IERS through a conventional terrestrial reference frame formed by SLR, LLR, VLBI and GPS stations is presented. In particular its origin, scale, orientation and evolution with time are reviewed, taking into account relativistic and deformation effects.

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Journal articles on the topic 'Celestial orientation'

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