a telescope for viewing the sun, adapted to protect the eye of the viewer from the sun's glare.
Origin of helioscope
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for helioscope
To the "helioscope" employed by Father Scheiner two centuries and a quarter earlier, a species of micrometer was added.A Popular History of Astronomy During the Nineteenth Century|Agnes M. (Agnes Mary) Clerke
A few words must here be said concerning the helioscope, which on more than one occasion played a prominent part in this war.The Story of the Zulu Campaign|Waller Ashe