Source : Webster's Revised Unabridged Dictionary (1913)

Helioscope \He"li*o*scope\, n. [Helio- + -scope: cf. F.
   h['e]lioscope.] (Astron.)
   A telescope or instrument for viewing the sun without injury
   to the eyes, as through colored glasses, or with mirrors
   which reflect but a small portion of light. --
   {He`li*o*scop`ic}, a.