Abstract

Polarizing plates, made of polarizing film cemented between glass, provide a new and convenient filter for the navigator’s sextant. The celestial filter consists of two polarizing plates, one or both of which may be interposed into the optical path, and when both are in position, one may be rotated with respect to the other to yield the desired reduction in light intensity of the celestial object. The combination is a rapidly adjustable variable filter. The horizon filter likewise consists of two polarizing plates. These fulfill a double function. One plate is set with axis of polarization vertical; this usually sharpens the sea sky horizon and diminishes the glare of the sun path. The addition of the second plate, which is rotatable, provides a rapidly adjustable variable filter.

© 1936 Optical Society of America

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