The Equinox : Roots of Astronomy

In 1911 Marcel Castanet discovered a reindeer bone carved with cup-marks in the Aurignacian site of Blanchard shelter whose geographic coordinates are: central axis azimuth: 270deg; latitude: 44deg59\´59.9"N, longitude: 01deg06\´03.3"E. About 50 years after, A. Marshack interpreted this unit as a "lunar calendar". This hypothesis was not sufficiently supported to be credible. By supposing that the figure was a lunar-day notation, it would have been of primary importance to envisage that this figure being serpentine, because the observations had obligatorily been carried out always from the same point. The horizontal coordinates of this point are the essential key to answer Marshack\´s question: "Did the sinuous central figure of the principal face represent one particular period?" and why didn\´t he try to consider and calculate the observations of the lunar coordinates from the archaeological site of the discovery? This work-field methodology has allowed us to definite the annual period of observation with the help of the 2004 lunar coordinates calculated for this precise place by the "Bureau des Longitudes" and so to evaluate some astronomical knowledge 35 000 years ago.