4/2/2023 0 Comments Northern skychartThe two epochs connected with the map (Ptolemy - 6° 40' and Ptolemy - 55°) are closely connected with the precession theory introduced by Copernicus in his De Revolutionibus in 1541. However, astrologers also showed an interest in the Anno Mundi.Ĩ. This could point to an illustration in books on Chronology. Jewish and Christian sources cite for this value 3761 BC and 3952 BC. It seems that the modern maker had some reason to make the beginning of constellation Aries coincident with the equinox. The first date is close to Eudoxus but his equinoxes are not at Pt-6° 40'. The epoch Pt-6° 40' and Pt-55° are equivalent to about 340 BC and 3800 BC, respectively. The date of the map can only be deduced from the historical problem it intents to illustrate. There are however to my knowledge no examples known of in the projection of the present map.ħ. The map is an early example of the type of modern maps one finds in publications of the works of Manilius and Hyginus. The map shows only the classical Ptolemaic constellations because it served a historic purpose. This northern 'copy' was extended to southern constellations with variations in iconography.Ħ. The iconography of the constellation north of the ecliptic is a close copy of the northern map by Dürer of 1515 which is also a stereographic projection from the north ecliptic pole. There are numbers which mark the longitude fore the epoch Pt-6° 40' inside the innermost scale but these numbers do not agree with the division of the scale.ĥ. The outermost scale numbers signs but neither scale seem to belong to the elliptic for one of the two epochs marked on the map. There are two scales at the border of the map. For this epoch the colures, equator, north polar circle and the tropics are drawn by dotted circles.Ĥ. If we estimate 'the little more' as 20', we arrive for this second epoch at Pt-55°. There is another epoch indicated in the map which is about 48° and 'a little more' from the main epoch. For this epoch Pt-6° 40' the colures, equator, north polar circle and the tropics are drawn by full circles.ģ. This suggests that the maker worked with Ptolemy. The stars gamma Ari and alpha Vir, which according to the Ptolemaic stars catalogue have longitude of respectively 6° 40' and 176° 40', are on the map at respectively zero longitude and 170°. It extends from ecliptic latitude +90° to about -50° (the star delta CMa with a Ptolemaic latitude -48° 45' is marked).Ģ. The map is a stereographic projection with the north ecliptic pole in the centre (not to be confused by the more common astrolabe which is a stereographic projection with the north equatorial pole in the centre). The following information related to this chart is kindly provided by Elly Dekker:ġ. Consequentially the paper was manufactured in or before 1569. The same paper was used for a document from Vienna dated 1569. It is printed on a paper with a watermark identified as #24004 from Piccard watermark database. We could not locate any bibliographical information about this engraving. A large, scarce 16th century celestial chart of the northern sky.
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