color index

American  

noun

Astronomy.

1. the difference between the apparent photographic magnitude and the apparent visual magnitude of a star.

2. the difference between the magnitudes of a star in any two spectral regions.

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Etymology

Origin of color index

First recorded in 1920–25

Example Sentences

A color index might lead reporters with an appetite for eye-catching headlines to produce misleading stories of an out-of-control border.

From Washington Times

Tall, dark Howard Ketcham, 33, began his color career in an advertising agency, joined the automotive paint division of du Pont de Nemours & Co.. reduced 13,000 body colors to the 600 listed in the Automotive Color Index.

From Time Magazine Archive

Last, but not least, the translucent tissues, the semi-transparent skin, barely veiling the pulsating mesh of myriad blood-vessels, is a superb color index, painting in vivid tints—"yellow, and ashy pale, and hectic red"—the living, ever changing, moving picture of the vigor of the life-centre, the blood-pump, and the richness of its crimson stream.

From Project Gutenberg