Helioscope

A helioscope is an instrument used in observing the Sun and sunspots.

The helioscope was first used by Benedetto Castelli (1578-1643) and refined by Galileo Galilei (1564–1642).

The method involves projecting an image of the sun onto a white sheet of paper suspended in a darkened room with the use of a telescope.

[1][2] The first machina helioscopica or helioscope was designed by Christoph Scheiner (1575 –1650) to assist his sunspot observations.

[3] In the context of modern astroparticle physics, the term helioscope can also refer to an experiment that seeks to observe hypothetical particles (such as the axion) produced inside the sun.