Spectroscope c.1900 A Kruss, Hamburg Germany Brass, cast iron, glass, bakelite Used to study the wavelength of light 12-1/2” high Spectroscopes are used to study the various wavelengths of a source of light. They incorporate a prism in the light beam path that splits the light into its fundamental wavelengths. Each wavelength appears as a different colored stripe in the eyepiece. Since each element has a unique wavelength, spectroscopes were used to study the purity and chemical makeup of many elemental materials.
 Spectroscopes are also one of the most important contributors to the field of astronomy. Spectroscopy, the use of light from a distant object to understand what the mineral content is, could be the single most powerful tool astronomers have used. Without spectroscopes, we would know very little about the makeup of the bodies in the universe. This spectroscope is 12-1/2” high. It is supported by a black three-legged steel base. The brass is finished in a golden lacquer. The circular central chamber houses the original prism. The prism edges are machine-rounded and the long side is painted black. The two short sides have been ground to control the light’s direction through a circular window in each of the prism’s short sides. There are three brass outer tubes that enter this prism chamber. The viewing telescope which is 8” long is used to observe the spectrum. There are three motion controls mounted on this tube. There is a dial indicator with 90 equal silvered graduations per revolution read by a fixed pointer. When the dial indicator is rotated, it moves a glass slide slowly across the inside of the eyepiece. Finely etched into the glass slide are crosshairs in an “X” formation. The middle motion at the top of the telescope drives a rack and pinion field of view focus. The third and innermost motion is also a thumbscrew dial indicator with 0 to 90 equal graduations per revolution read by a fixed pointer. It controls the position of the prism. The 6” long collimator has two adjustable slits for the observation of the incoming light which passes through one or two slits and then is directed and focused through the collimator to the prism where the spectrum can be observed by the above-referenced viewing telescope. Both slit controllers are read by dial indicators with the same specifications as the indicator on the viewing telescope except one is read by a vernier that further splits each one of the 90 graduations by 10. Both motions control the width of their respective slits. Each slit projects light to 1/2 of the view field - upper or lower. This allows the user to analyze two different light sources at the same time for comparison purposes of a known standard light source spectrum to an unknown spectrum. It is also possible to combine the light sources into a single spectrum.

 The third brass tube is fixed and has a fixed slit at the outer end. When a light travels through the slit, it projects a measurement reticule across the spectrum in the viewing telescope. The measurement reticule appears as a straight-lined fine rule, numbered from 1 to 30 with 10 lines between each number or 300 total lines.
 There is an original pivoting lamp bracket to which one later leg has been attached a with low-voltage DC light bulb. 

For a portable instrument, this is well-designed and it is extremely accurate. All the functions work and it is in excellent original condition.

“A KRUSS HAMBURG” is engraved on the instrument. Circa 1900. 
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Link to the history of A.KRÜSS Optronic which has been in business since 1796: https://www.kruess.com/en/company/about-us