colour index

noun

1. astronomy the difference between the apparent magnitude of a star measured in one standard waveband and in a longer standard waveband, indicating its colour and temperature
2. geology the sum of the dark or coloured minerals of a rock, expressed as a percentage of the total minerals
3. chem physics a systematic arrangement of colours according to their hue, saturation, and brightness

Example Sentences

Instead of s there may also be used another expression for the colour, called the colour-index.

From Project Gutenberg

The difference between the photographic and the visual magnitudes is called the colour-index (c).

From Project Gutenberg

From each catalogue of visual magnitudes of the stars we may obtain their photographic magnitude through adding the colour-index.

From Project Gutenberg