Planisphere, "Malby's New and Improved", dated 1858, by Malby & Sons, 37 Parker Street, Little Queen Street, Holborn, varnished card in fabric sleeve, with additional hand-drawn celestial map

Dated 1858, this planisphere was made by the London publishers, Malby & Sons. The square device made of paper and card is a map of the heavens. It allows the user to display the appearance of the sky at any time of night or day throughout the year. The positions of the stars are plotted on a flat surface using the mathematical technique of stereographic projection. A square mask with a circular opening covers the celestial map showing only those stars visible at the time and season indicated. The planisphere is also provided with a rule and circular scale on the edge of the aperture to indicate the elevation and direction of the stars shown.