Astronomical Images : The motion in latitude of the eccentric of Venus

Peter Apian

Astronomical Images

This Venetian edition of Peuerbach's Theoricae novae was copied from Apian's 1528 edition, printed in Ingolstadt. Subsequently, the work went through several further editions. Apian's edition added new woodcuts as well as notations to some of those from earlier editions. Some errors in the woodcuts in the 1528 edition were repeated in this Venetian edition of 1537. In the first editions of the Theoricae novae there is no diagram specifically devoted to Venus. Oronce Fine, first in his edition of Franciscus Capuanus' commentary on Peuerbach (Paris, 1515), then in his edition of the Theoricae novae (Paris, 1525), was the first to illustrate the short chapter De Venere. This image of the intersection of the plane of the eccentric of Venus with the plane of the ecliptic (and of the eccentric of the Sun) originated in a figure of the first edition of Sylvester de Prierio's commentary on Peuerbach (Milan, 1514). This figure is inserted near the passage concerning the movement of the epicycle of Venus 'in longitude and latitude' (in longum et in latum). As there is no legend, nor comment, it can be assumed that it concerns the latitude of the epicycle. Oronce Fine reproduced the figure in his own edition of the commentary of Sylvester de Prierio (Paris, 1515), where the layout makes clear that it concerns the latitude of the eccentric of Venus. Apian then introduced a clumsy imitation of it in his own edition. In the original De Prierio figure there are two images of the intersecting planes transfixed by their axes. In the first image the axis of the plane facing the reader is low in front and high behind, while the axis of the other plane is high in front and low behind. In the second image, this is the reverse. Thus, the swinging to and fro of the plane of the eccentric is suggested. In the Apian edition there is only one image, no explanation is given, and the axes do not seem to be perpendicular to their planes. Thus, the diagram is nothing better than a vague illustration of Peuerbach's text: the movement eastward of the eccentric of Venus 'is made about its imaginary axis, whose poles approach and recede from the poles of the zodiac on each side, on account of the other motion of the eccentric in latitude, concerning which something will be said later' (sit autem motus huius deferentis in longitudinem super axe eius imaginario, cuius poli accedunt et recedunt a polis zodiaci in utranque partem proter motum alium in latitudinem, de quo post dicendum erit). As a consequence, 'the apogee of the eccentric does not cross the ecliptic, but â?¦ sometimes declines to the south, and sometimes to the north' (aux eccentrici non eclipticam non transeat, verum â?¦ quandoque ad Meridiem, quandoque ad Septentrionem declinat). Translated quotations of Peuerbach's Theoricae are from Aiton (1987).