This is referring to the angle of the Sun in the sky.

None of the images on this site have been lit by bright, direct sunlight. Instead, they were taken when the sun was either very low in the sky or below the horizon.

Light from a low sun is softer, with reduced contrast. This period, known as the Golden Hour, bathes the landscape in warm tones and rich colour saturation. Clouds can glow with pinks and yellows, reflecting their hues onto the land below. As the sun dips below the horizon, its light becomes even warmer until it finally fades away.

This is followed by the Blue Hour, when the warmth disappears, yet the landscape remains visible in a cooler, more subdued light. Then comes twilight and night, when illumination comes from the stars, distant galaxies, charged particles, and artificial sources.

At dawn, the cycle reverses—night gives way to the Blue Hour, followed by the return of the Golden Hour.