Scheiner's helioscope, after a drawing in
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 on
the 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.
Scheiner
Galileo
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