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Sparavigna, A. (2017). Software applied to archaeoastronomy:  SunCalc and MoonCalc at the Torhouse Stone Circle. PHILICA.COM Article number 1134.

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Software applied to archaeoastronomy: SunCalc and MoonCalc at the Torhouse Stone Circle

Amelia Carolina Sparavignaunconfirmed user (Department of Applied Science and Technology, Politecnico di Torino)

Published in enviro.philica.com

Abstract
In this paper, for the analysis of a stone circle and possible links to the path of the sun and the moon we use SunCalc.org and MoonCalc.org. The stone circle is that of Torhouse, three miles west of Wigtown, Scotland. As we will see, it was an ancient astronomical observatory.

Article body



Software applied to archaeoastronomy:  SunCalc and MoonCalc at the Torhouse Stone Circle

Amelia Carolina Sparavigna
Politecnico di Torino

In this paper, for the analysis of a stone circle and possible links to the path of the sun and the moon we use SunCalc.org and MoonCalc.org. The stone circle is that of Torhouse, three miles west of Wigtown, Scotland. As we will see, it was an ancient astronomical observatory.

In some previous papers (see for instance [1-5]), we have applied software, freely available on the web and easy to use, for the investigation of the alignments of building and monuments along the sunrise on specific days of years, such as those of solstices or of the zenith passage of the sun (in the tropical zone). Software used comprises Sollumis.com, SunCalc.net and SunCalc.org.  These apps are giving, besides other information, sunrise and sunset directions on the satellite images of Google Earth.  Of course, to be more specific in the analyses, it is also necessary to investigate the profile of the horizon and the local elevation of the area where the monument is places, but this can be easily obtained by means of Google Earth (see an example in [6]).  Software SunCalc.org has an interesting feature, which can be useful for the investigation of the megalithic structures: it is able of simulating the shadows. In [7], we applied the software to the Bronze Age stone circle of Long Meg and her Daughters, near Penrith in England, to simulate the shadow of Long Meg menhir.
For the moon and the simulation of its cycle of major and minor lunar standstills we have software such as the Photographer’s Ephemeris and MoonCalc.org (see them used in [8-10]).  Our natural satellite has an apparent motion in the sky, which is more complex than that of the sun. We have that the sunrise direction oscillates between the two solstice positions during a year, whereas the moon does the same during a nodal period (about 27 days). Moreover, the moon has a period – the lunar standstill period (18.613 years) – during which the values of the extreme directions (standstills) are changing. In this manner there are major and minor standstills, of which we can calculate moonrise/moonset directions. These directions are depending on latitude. For a latitude of about 45°, like that of Torino for instance, we have that the minor and major northern moonrise azimuths (directions) are 47.40° and 65.65° (angles are given from true north). The minor and major southern moonrise azimuths are 116.35° and 132.58°. The azimuths of sunrise on summer and winter solstices are between these lunar azimuths.
An easy manner to see the behaviour of the moon is that of using the Photographer’s Ephemeris for the place or town where the user lives. Or, if calculations are preferred, formulas are given by Jürgen Giesen at his web site http://www.geoastro.de/ sunmoonpolar/ index.html#Mondwenden. The reader can find detailed discussion and apps for the simulation of the moon apparent motion. Another useful software is CalSky – www.calsky.com/cs.cgi – a web based astronomical calculator used by astronomers to plan observation. We used it for [11].
In this paper, for the analysis of a stone circle and possible links to the path of the sun and the moon we use SunCalc.org and MoonCalc.org. The stone circle is that of Torhouse, described in detail by the Photographers Resource [12], an important web resource for the study of the stone circles in Great Britain. The web site gives an Introduction to Stone Circles and discussion on the purpose of them. Let us use the page on the Torhouse Stone Circle [12] for discussing it as an ancient astronomical observatory.
The circle is 19 m across and has 19 rounded granite boulders varying from 0.6 m to 1.45 m high. The stone circle is on a raised platform made from smaller stones. Inside the circle, we find three upright stones (Figure 1). “Its central stones are in an alignment facing Cairnsmore (summer solstice sunrise) and the Fell of Barhullion (winter solstice sunset)” [13]. The stone circle was crated in the period of time from 2000BC to 1500BC.
 

About the link of the circle to astronomy we read also in [13] that the “19 stones is the same number of stones as a number of other stone circles, see Merry Maidens, Cornwall. It has been suggested that 19 would have been an important number for a people who celebrated the path of the moon through the great lunar cycle”. The lunar cycle mentioned is that of the major lunar standstills (for a discussion, see https://en.wikipedia.org/wiki/Lunar_standstill). Let us visualize the mentioned alignments. Let us start from the sun. Here the results for solstices in the Figures 2 and 3.  

 

 

 

In the Figures 2 and 3 we can see the simulations obtained by means of SunCalc.org of the summer and winter solstice. The pivot used for the directions is the southern of the central stones. These stones are important for another simulation, that of the shadows, as we made in [7] (the role of the shadows in Long Meg and her Daughters was pointed on by S. Hood in [14]). In the Figure 4, we are giving a simulation of the shadow of the pivot.

 

 

For what concerns the moon, we can use MoonCalc.org. Here in the following Figure 5 the simulations on a major lunar standstill.

Of course, the stone circles in Great Britain had been deeply investigated by archaeologists and archaeoastronomers. What we have made here, and in previous papers,  is that of showing a method which any observer can easily repeat using freely available software. It is enough to consider simulations on solstices and lunar standstills for a preliminary astronomical analysis. For alignments towards the rising of  stars, Stellarium software can be easily used [15].

References
[1] Sparavigna, A. C. (2012). The solar towers of Chankillo. arXiv preprint arXiv:1208.3580.
[2] Sparavigna, A. C. (2012). The Chinese Pyramids and the Sun. arXiv preprint arXiv:1211.0915.
[3] Sparavigna, A. C. (2013). The Gardens of Taj Mahal and the Sun. International Journal of Sciences 2013 (11). Available at SSRN: https://ssrn.com/abstract=2573618
[4] Sparavigna, A. C. (2014). Solstices at the Hardknott Roman Fort (December 17, 2014). PHILICA Article number 442. Available at SSRN: https://ssrn.com/abstract=2745184
[5] Sparavigna, A. C. (2017). The Zenith Passage of the Sun and the Architectures of the Tropical Zone. Mechanics, Materials Science & Engineering MMSE Journal. Open Access, 2017, 10 (May), pp.1-12. 〈hal-01519183〉
[6] Sparavigna, A. C. (2016). The Italic Sanctuary of Monte Torre Maggiore and the Sky (December 18, 2016). Available at SSRN: https://ssrn.com/abstract=2887082 or http://dx.doi.org/10.2139/ssrn.2887082
[7] Sparavigna, A. C. (2017). The Role of the Shadows in a Bronze Age Stone Circle (October 14, 2017). Available at SSRN: https://ssrn.com/abstract=3053130
[8] Sparavigna, A. C. (2016). Augusta Emerita and the Major Lunar Standstill of 24 BC (July 10, 2016). PHILICA Article Number 635. Available at SSRN: https://ssrn.com/abstract=2807544
[9] Sparavigna, A. (2016). Astronomical Alignments of Ales Stenar along Sunset and Moonset Directions. PHILICA.COM Article number 663.
[10] Sparavigna, A. (2017). Alignment along the Moonrise on Major Lunar Standstills of the Pipers, the Pair of Standing Stones at St Buryan. PHILICA Article number 1127.
[11] Sparavigna, A. C. (2016). Astronomy and Tidal Analysis Applied to the Study of Julius Caesar's Commentarii (August 2, 2016). Available at SSRN: https://ssrn.com/abstract=2817327 or http://dx.doi.org/10.2139/ssrn.2817327
[12]  www.photographers-resource.co.uk
[13] Torhouse Stone Circle.   www.photographers-resource.co.uk/ a_heritage/ancient/ stone_circles/ LG/ Torhouse_stone_circle.htm
[14] Hood, S. (2004). Cumbrian stone circles, the calendar and the issue of the Druids. Transactions
of the Cumberland and Westmorland Antiquarian and Archaeological Society, 3(4), 1–25.
[15] Sparavigna, A. C. (2016). The Stellarium Planetarium for the Simulation of the Astronomical Landscapes of Ancient Stargazers (November 19, 2016). Available at SSRN: https://ssrn.com/abstract=2872676 or http://dx.doi.org/10.2139/ssrn.2872676

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Sparavigna, A. (2017). Software applied to archaeoastronomy: SunCalc and MoonCalc at the Torhouse Stone Circle. PHILICA.COM Article number 1134.


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