Conditions are given for the performance requirements for a high speed spectrograph objective to be used primarily for the Raman effect in the region 4358 to 5000A. A formula is given for the construction of such an objective at a speed of f/2.0. This objective has a flat tangential field and gives extremely sharp definition. With slight retouching of the back of the second flint component perfection of definition can be achieved in lenses up to 12 in. focal length. A correction to the formula is given to render the field flat with all spherical surfaces. The unretouched system works perfectly satisfactorily up to an 8 in. focal length. The trignometrically calculated aberration curves are given for a lens of 10 in. focal length.
The formula is given for construction of a 10 in. focal length f/3.5 three element lens. The design consists of a telescope objective followed by an aplanatic element. Aberration and performance characteristics are given and discussed.
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