'Used to measure properties of light over a specific portion of the electromagnetic spectrum - usually in spectroscopy for producing spectral lines and measuring their wavelengths and intensities. Scale: 170mm diameter - divided 0 to 360'' x 1'' - independently rotatable with locking screw. A spring loaded vernier scale attached to the telescope mount provides readings 0.1'' (6 minutes of arc). Collimator: Mounted on fixed pillar with axis adjustment. Objective lens has 150mm focal length - an aperture of 212mm - and is carried in spiral focusing system. Unilaterally adjustable slit 6mm long. Telescope: Mounted on moveable pillar with fine adjustment - locking screw - and axis adjustment. Objective lens has 170m focal length - 21 mm - aperture and is carried in a spiral focusing system.. Prism table: The table is provided with three levelling screws and has lines marked to assist placement of the prism. Mass: 5.4 kg. Standard accessories supplied: 1 prism clamp for prisms up to 40mm high - 1 diffraction grating holder - aperture 25 x 25mm - 1 small screwdriver - 1 tommy bar for axis adjustment. Comprehensive setting up instructions are also included. Does not include prism.'