Scheiner's helioscope, after a drawing in Scheiner's Rosa Ursina, reproduced from The history of the discovery of the solar spots, in Popular Astronomy, 24, W.M. Mitchell, 1916.
While Galileo largely abandoned systematic sunspot observations following the publication of his Three letters on Solar Spots, Scheiner devoted himself fully to sunspot observations. He improved onthe projection method of Galileo and Castelli by designing a specialized telescopic solar projection instrument, which he called heliotropii telioscopici (helioscope being a rough contracted translation). This represent the earliest known equatorially mounted instrument.