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

The color index and how the eye and film “see” colors are discussed.

From Textbooks • Oct. 13, 2016

Why use a color index if it ultimately implies temperature?

From Textbooks • Oct. 13, 2016

A color index of a star is the difference in the magnitudes measured at any two wavelengths and is one way that astronomers measure and express the temperature of stars.

From Textbooks • Oct. 13, 2016

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 • Apr. 22, 2016