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Astronomical source of orientation of a monument

Astronomical source of orientation of a monument

For nearly ten thousand years, human beings have been engraving in stone
the key moments of our life on Earth, in connection with the solar and stellar cycles.
So that most of the megalithic structures and monuments of the Antiquity
point towards the position of the Sun or a star at its rising or setting.
With the help of modern tools, let's determine the identity of the celestial object targeted ...

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point In brief

Since the appearance of our species on Earth, humans and stone have had a very special relationship. So that prehistory, which began about three million years ago, is divided into periods called Paleolithic, Mesolithic and Neolithic. Both their respective names and their succession underline the evolution of our relationship with stone - from the creation of the first lithic tools to their polishing through their geometrisation and microlithisation, for essentially everyday purposes: hunting, butchering, clearing, ploughing, harvesting, construction, etc. Logically, the use of stone to record the occurrence of events that have a significant impact on our life on Earth - such as the succession of the seasons of the year - follows. Thus, most of the megalithic complexes are oriented towards the positions of sunrise or sunset at various key times of the year: winter solstice, spring and autumn equinoxes, or summer solstice. The same applies to the stone monuments erected during Antiquity... unless, for cultural or worship reasons, some particularly bright stars were sometimes preferred to the Sun?

Megalithic complex of Nabta Playa in Upper Egypt
This megalithic complex was erected during the fifth millennium BC on the site of Nabta Playa in Upper Egypt.
Its study has highlighted the existence of an alignment towards the rising sun on the day of summer solstice.


This software designed during my PhD thesis invites you to accurately determine the astronomical source of orientation of any monument erected since the year 4713 before our era. To do so, it uses data issued from the Hipparcos catalog (coordinates of 5043 stars visible with the naked eye), combines various algorithms of astrometry (relative to the positioning of the stars on the sky) and photometry (relative to the brightness of the object sighted and the local visibility conditions) borrowed from the scientific publications mentioned below.

The access to the user interface of this software is made on payment : 45 euros, which can be paid via the Paypal secured paiement system (payment by PayPal account or by credit card). This amount includes an unlimited access to the user interface and a free access to any future updates. Free tests of this software are available within the Culture Diff' Client Area.

Price : 45,00 euros

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point In detail ...

The erection of the very first stone structures (menhirs, dolmens, cromlechs, circles and alignments of standing stones, etc.) dates back to the fifth millennium before our era. Most of these megaliths or megalithic complexes present a particular astronomical orientation: solar, lunar, or even stellar. The same applies to later stone monuments - temples, tombs, pyramids, erected by the Egyptian, Mesopotamian, Mayan, Inca civilizations, as well as the various peoples who followed them.

Megalithic complex of Nabta Playa in Upper Egypt
In 2008, the megalithic complex of Nabta Playa was moved to the garden of the Nubian Museum in Aswan
in order to preserve the orientation of each stone and the alignments they form.

This software leading to determine the astronomical source of any monument erected since 4713 before our era (beginning of the Julian era in astronomy) has been conceived on the basis of the most recent algorithmic developments, both in astrometry (branch of astronomy dedicated to the determination of the positions and motions of the stars) and in photometry (branch of astronomy related to the measurement of the energy carried by the light particles emitted by distant stars). Since it takes into account the local geographical (latitude, longitude and altitude of the construction site) and meteorological (temperature and humidity of the ambient air) conditions, as well as the visual acuity of the observer, i.e. our ability to distinguish a bright spot against the background of a night or twilight sky, this unique software will provide you with results that are in line with the observed reality: a list of stars visible to the naked eye whose position of appearance in the eastern sky or culmination in the local meridian or disappearance from the celestial vault, in the night or twilight sky, explains the astronomical orientation of the monument under consideration - of its main axis or of one of its faces. The heliacal rising or setting of a star was sometimes preferred to its appearance or disappearance from the night sky, in fact - mainly for worship reasons.

Astronomical orientation of the megaliths of Nabta Playa

The stone circle of Nabta Playa has two alignments: one parallel to the north-south axis, the other towards the rising position of a star or the setting position of another star.
This software will allow you to identify the one or the other star.

Astronomical orientation of the megaliths of Nabta Playa

This standing stone in the megalithic field of Nabta Playa seems to point towards the (upper or lower) culmination position of a star in the local meridian.
This software will allow you to determine the star targeted.

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This software designed during my PhD thesis invites you to accurately determine the astronomical source of orientation of any monument erected since the year 4713 before our era. To do so, it uses data issued from the Hipparcos catalog (coordinates of 5043 stars visible with the naked eye), combines various algorithms of astrometry (relative to the positioning of the stars on the sky) and photometry (relative to the brightness of the object sighted and the local visibility conditions) borrowed from the scientific publications mentioned below.

The access to the user interface of this software is made on payment : 45 euros, which can be paid via the Paypal secured paiement system (payment by PayPal account or by credit card). This amount includes an unlimited access to the user interface and a free access to any future updates. Free tests of this software are available within the Culture Diff' Client Area.

Price : 45,00 euros

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point Bibliography

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