Crimson & Blue & Magenta

Crimson (dark, vivid warm — the hydrogen-alpha emission wavelength of ionized gas nebulae), Blue (pure electric cool — ionized oxygen [OIII] emission), and Magenta (pure, non-spectral, warm-cool bridging — the combined-channel composite of hydrogen-alpha and [OIII] emission) create the most astronomically specific and most cosmically extraordinary palette — the three primary emission channels of modern deep-sky astrophotography.

The palette is the visual world of Hubble Space Telescope astrophotography — specifically the Hubble Palette (also: the SHO palette — for Sulfur-Hydrogen-Oxygen — the false-color image processing technique used in the most celebrated Hubble Space Telescope images). The Hubble astrophotography palette: the deep vivid crimson of the hydrogen-alpha emission (Hα — the specific red emission line of ionized hydrogen at 656.28 nanometers wavelength — the most intense and most characteristic emission line of nebulae containing hot ionized gas — specifically the H II regions — areas of ionized hydrogen surrounding young, hot, massive stars — the most visually dominant emission in the most celebrated nebula images including the Eagle Nebula — 'Pillars of Creation' — and the Orion Nebula); the pure electric blue of the doubly ionized oxygen emission ([OIII] — the forbidden emission line of oxygen that has lost two electrons, at 500.7 nm wavelength — the specific pure blue-to-blue-green of the most vivid and most spectrally brilliant nebular emission line); and the pure magenta of the image compositing technique (in the standard Hubble Palette, when the Hα channel — red — and the [OIII] channel — blue — are combined, the resulting composite color in areas of mixed emission is the characteristic magenta — where both hydrogen and oxygen emission are present simultaneously).