This is a beauty! Portable and precise, the instrument provides direct wavelength readings of visible spectrum from 400nm to 750nm with each scale division representing 5nm. The spectrum is viewed in the plane of scale and for error free readings, the D-line (wavelength of sodium light) on the scale can be adjusted.
Great for demonstrating spectra from any visible light source. Precision made heavy duty stainless steel construction with an Amici type 3-element prism assembly with angle dispersion C-F 5 degrees, variable optical slit and adjustable eyepiece. Easy to use: Optical slit adjusts by rotating the knurled end piece, and focus for both the scope and wavelength scale is slip type. Contrast and resolution of the spectrum is changed by adjusting the slit opening. Both emission and absorption spectra can be viewed. Compact 4-1/4" inches long by 1 inch diameter on the slit end and 1-3/4" wide on the eyepiece end. We have seen similar ones selling for $350.00 online. Lots of uses including gem studies. New with wood case. Wollensak quality optics since 1899.
Here's a link to some calibration information provided by one of our customers: http://www.prc68.com/I/ML-OSA.shtml#L3524D. Thanks Brooke