Concerning the Construction and Use of a Globe, Planisphere and Device to Show More Clearly the Celidography and Other Observations of Venus

Abstract

I. The construction of a globe, planisphere and armillary device to be based on the observations of Venus’ poles, axis of rotation and equator. II. The equator was seen clearly and almost coincided with or lay along the terminator on March 1st 1726. III. This is shown from the diagram of observations. IV. The point on the Ecliptic must also be sought which is crossed by the plane produced through Venus’ axis of rotation and the Sun that is at right angles to the plane of Venus’ eight-month orbit round the Sun. V. On the diagram of the planisphere showing Venus’ orbit round the Sun, with the eye of the spectator placed at the pole of the Ecliptic, this is explained more clearly. VI. Observations made in 1726 in the month of February indicate that the plane produced through Venus’ axis of rotation and the Sun meet the Ecliptic at about the 20° points in Leo and Aquarius. VII. After determining the point of the Ecliptic which cuts that plane which represents the solstitial Colure of Venus, and showing the amount of 15° by which the axis of rotation is raised at the North pole 15° above the plane of the Ecliptic and depressed 15° below at the South pole, the construction of an armillary device is proposed to show all Venus’ phases. VIII. That armillary device can be adapted to both systems, that of Tycho and that of Copernicus. IX. The same effect achieved through a planisphere, the construction of which for either system and use is demonstrated. X. The use of another little machine to be fitted to the planisphere is explained, so as to represent accurately the different phases and markings to be seen on Venus.