Lunar Observatories of Megalithic Man

Thom, A.

doi:10.1038/2121527a0

Cited by 3 publications

(10 citation statements)

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“…33 Thus, we can determine the approximate near-contact path by simple examination of topographic heights on a contour map or digital elevation model, 34 identifying those portions of the ray path that are within a chosen height above the ground. To test this model against realistic examples, I computed the length or the path at a given height above the ground (Table 2) for three ethnographically attested horizon markers at the Hopi Pueblos, 35 five representative horizon profiles selected from among those which Alexander Thom used as the basis for his claim of highly precise lunar observations, 36 and a site at Stonehenge where strong refraction near the surface had led the Thoms to postulate the need for a graze correction. 37 These can be compared with the case of refraction at a level surface discussed by Schaefer and Liller.…”

Section: The Influence Of Local Topographymentioning

confidence: 99%

Archaeoastronomy and Refraction Near the Earth’s Surface

McCluskey

2017

Journal for the History of Astronomy

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Empirical studies of refraction based on observations of sunset or sunrise over the ocean or other level1 surface have indicated that refraction is too large and variable to support precise archaeoastronomical observations. On the other hand, ethnoastronomical studies of Puebloan sun-watching over elevated horizon markers have revealed observations near the solstices consistent to 1.2 days or 2–6 arcminutes in azimuth. A comparison of the different geometrical configurations of these two types of observations, of the interactions of these geometries with the strong and changing temperature gradients near the surface and with the specific local topography resolves this paradox by demonstrating that observations over a level horizon obtain near-surface refraction one to two orders of magnitude greater than refraction over elevated horizon markers.

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Section: The Influence Of Local Topographymentioning

confidence: 99%

Archaeoastronomy and Refraction Near the Earth’s Surface

McCluskey

2017

Journal for the History of Astronomy

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“…Because of the remarkable accuracy with which the site at Ballochroy can be operated one thinks of it as easily the best megalithic solstitial observatory [7]. This is only one of the large number of sites with indications for the solstitial sun, but other dates in the calendar were also important.…”

Section: Astronomymentioning

confidence: 99%

Megaliths and Mathematics

Thom¹

1966

Antiquity

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We are hearing more and more about the mathematical and astronomical aspects of megalithic monuments, a subject that has often been ventilated in the pages of this journal. Now we have a book by G. S. Hawkins andJ. B. White entitled Stonehenge Decoded which is described as 'the account of how computer analys& revealed the stones as a sophisticated astronomical observatmy' ; this will be reviewed by Professor R. J. C. Atkinson in our next issue. Dr Alexander Thom was Professor of Engineering Science in Oxford from 1945 to 1961, and now, living in retirement in Ayrshire, is an Emeritus Fellow of Brasenose. All his life he has been interested in the measurements used by the megalith builders and has written many articles on this subject. Here he summarizes for readers of ANTIQUITY his general views on this whole vexed matter.is becoming apparent that megalithic man

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“…Archaeoastronomy often concerns itself with the contention that some ancient monuments are aligned with the rising and setting of celestial objects. Two well-known illustrations of this paradigm are the alignment of the avenue at Stonehenge with the midsummer sunrise (Hawkins 1965) and the precise alignments of many British megalithic sites toward significant moonrise positions (Thom 1971). To make a connection between the monument and the sky, an archaeoastronomer must be able to translate an azimuth measured at the site into a declination on the sky.…”

Section: Introductionmentioning

confidence: 99%

“…Archaeoastronomers have considered the effects related to simple temperature and pressure changes in the atmosphere. Their analysis adopts some equation for the temperature and pressure dependence of refraction (e.g., Allen 1973;Thom 1971; or the Astronomical Almanac).…”

Section: Introductionmentioning

confidence: 99%

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Refraction near the horizon

Schaefer

Liller

1990

PASP

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We have studied the variation of astronomical refraction near the horizon. We have collected 144 measurements of refraction from seven sites by three techniques and have found that the variation of refraction on the horizon is substantially larger than has previously been realized. The rms deviation of our observations is 0?16, while the individual measurements range from 0?234 to 1?678. At the 95% confidence level the total refraction should vary over a range of 0?64. This surprising result has five applications: First, the time of sunrise can only be predicted with an accuracy of 4 min, despite all the extreme accuracy of modern positional astronomy. Second, during a low-altitude solar eclipse (such as is the 1990 eclipse viewed from Finland), the size and shape of the edge of the umbra will vary in an unpredictable manner by perhaps several kilometers, so that attempts to measure the diameter of the Sun may have an unexpected accuracy limit. Contact times may vary by typically 0.1 sec. Third, refraction variation will set a fundamental limit on the accuracy of any claimed archaeoastronomical alignment. Fourth, methods for aligning the Great Pyramid of Cheops to an accuracy of 2' cannot involve near-horizon observations. Fifth, the historically important claim by A. Thom that British megalithic sites were used as accurate lunar observatories is shown to be wrong because the needed accuracy is much greater than can be obtained for long averaging intervals.

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Lunar Observatories of Megalithic Man

Cited by 3 publications

References 1 publication

Archaeoastronomy and Refraction Near the Earth’s Surface

Archaeoastronomy and Refraction Near the Earth’s Surface

Megaliths and Mathematics

Refraction near the horizon

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