This is a large metal direct-vision spectrometer. It consists of two tubes fixed at right angles to one another, supported above metal plates that are supported by three legs with slightly tapered bases.
Both tubes are of a similar length. One, the collimator, has a narrower section at the end which can be unscrewed from the larger tube. This section supports at the end a slit formed of two plates of metal fixed over the end of the tube. This slit’s width can be adjusted by turning a ridged knob attached to one side. This knob is affixed to a disk with graduations around the outside, labelled in tens. Next to this there is a small metal wedge acting as an indicator arrow. Affixed by a central pin over the top of the slit plates there is a metal disk with two rectangular holes cut in it, one smaller than the other. Over the top of this and attached to the same pin (although rotating independently), there is a metal arm with on one side a rounded section with a white rectangle image engraved on it, and on the other an arm which is raised slightly.
Where the two tubes meet there is a cylindrical cover with a flat lid; this is engraved with the instrument and maker’s name. This is screwed onto the support base, and likely covers a prism. The second tube, the eyepiece, is lined up against this cylinder at right angles to the collimator. It is supported by metal rings, the top half of which can be unscrewed to remove or replace the tubes. Torwards the end of the tube, there is a rod affixed to the exterior of the tube attached to a large ridged knob.
The end of the tube consists of narrower sections fitted inside on another. The first of these sections, fitted into the main tube, has a scale engraved on it, graduated in tens; “10” and “20” are visible. Next to this is another affixed rod with a knob. The smallest section is an eyepiece with a very small round hole in the centre, with a lens affixed to the inside.
Attached to the support for this tube there is a large wheel with a pair of scales engraved around the rim. One of these scales is linear, and labelled in tens from 0 to 980; the other scale is non linear and labelled in hundreds from 4200 to 7700, with the graduations of the higher numberes being smaller. This is attached to and rotated by a ridged knob affixed to a large rod which is parallel to the eyepiece tube. Also affixed by an adjustable arm to the support section is a magnifying glass that can be used to view the the scale on the wheel. The wheel is attached to a very large worm gear that fits against a rack-type gear section, affixed to the base that is underneath the prism cover, permitting fine adjustment of the prism’s angle.
Accession Number: 2019.ast.257
Spectroscope, Constant Deviation Wavelength Spectroscope, Spectromètre à deviation constante
Metal: Copper Alloy, Metal: Iron Alloy, Glass
Engraved on the lid of the prism case: “Spectromètre à deviation constante
gradué en longeurs d’onde
De M. Mrs A. Broca et Ph. Pellin
Ph. Pellin, Paris”
Length = 67, Width = 63.5, Height = 34.6
This spectrometer was used for the direct spectroscopic analysis of light.
Good: The metal surface of the legs and support plates of the instrument are rusted in spots across most of the surface of the instrument. This is especially severe on the rods attached to adjustment knobs, where almost all of the surface of the metal is rusty. The tubes and brass components of the instruments are in better condition, although there are dots and scratches of oxidation over all the components. The rim of the graduated wheel for adjustment of the prism is dotted with dark patches of oxidation, obscuring some of the lettering.
The prism seems to be present. The disk affixed in front of the slit is loose and may be missing some components.
The support underneath the eyepiece tube is cracked across its width close to the prism case. This crack has been mended by thick metal plates affixed to the side and base of the instrument with screws.
Associated Instruments:
Manufacturer: Ph. Pellin, Paris
Date of Manufacture: 1899-1923
This instrument was used at the David Dunlap Observatory in the 1930s. It was kept at the Observatory until 2009. Upon the sale of the Observatory in that year, it was moved to the University of Toronto’s Department of Astronomy & Astrophysics at the St George Campus. In 2017 it was moved to a new storage location in McLennan Physical Laboratories.
This spectrometer likely contains an original Pellin-Broca prism. This prism, which is four sided, permits the selection and analysis of a single wavelength from a spectrum.
Historical Notes: