© Science Museum / Science & Society Picture Library
Illustration taken from 'Iter Extaticum' (1660) by Athanasius Kircher (1602-1680). Kircher demonstrated that by placing a lens between a screen and a mirror which had been written on, a sharp but inverted image of the text would appear on the screen. By using a spherical water-filled flask as a condenser to concentrate the light, Kircher found that texts painted on the mirror's surface could be projected by light from a candle after dark. These demonstrations eventually resulted in the birth of the magic lantern. Sunspots, relatively cool areas on the photosphere, the visible surface of the Sun, were first observed teloscopically by Galileo in 1612.