Engraving of a spectroscope attached to a telescope for solar work, 1874.
© Science Museum / Science & Society Picture Library
Plate taken from Joseph Norman Lockyer's, 'Contributions to Solar Physics'. This engraving shows how observations of the Sun were conducted with a spectroscope attached to a telescope, and identifies the various component parts of the instrument by means of a key. A spectroscope is used to analyse the spectrum of solar radiation, with the light split into its constituent wavelengths by prisms.