For introductory class work. A Basic measuring instrument for quantitative spectroscopy experiment this instrument is mounted on a stable cast iron base with attached collimator and a rotating telescope platform and graduated circle. · · A 25mm Diameter achromatic optical system of Focal length 7” (178mm)with a 10x Ramsden eyepiece and cross line graticule. · An 8cm. Diameter prism / grating Table, fully adjustable with prism and grating holder and engraved ring pattern . Protected Circle 15.