Golden Sunsets

These are some of the sunsets we’ve enjoyed over the past few weeks. They rival some of the best AZ sunsets we’ve seen. All followed periods of rain, so there wasn’t much dust in the air, and clean air tends to produce more golden sunsets. The small amount of red you see is mainly the result of Rayleigh scattering.

In both photos the Sun is recently set behind the Hieroglyphic Mountains, 10 miles to the west. The view is from my south deck. The array of colors is beautiful, but the intensity of the golden hues is most striking. To get that gold color you need to be in a sunset “sweet spot” relative to the Sun. The gold color never lasts very long — maybe 20 to 30 minutes tops.

Rayleigh scattering increases with distance from the sunset point. That’s why the clouds turn reddish at greater distances, and why all sunsets end with red colors. The gold comes from a narrow overlap in the solar spectrum between red and green (which when mixed, paradoxically produce yellow). The RGB values for “gold” are 255, 215, 0 and that combination looks like this:

At least that’s what the “official” RGB gold looks like, but during that narrow sunset window it starts out brighter (like the last photo) and becomes duller (like the first photo) over time. As the Sun sinks farther below the horizon, Rayleigh scattering subtracts more of the shorter wavelengths until finally only red is left (like the second photo).

Sunsets are dynamic events, and if you only wander outside for a quick glimpse you’ll miss a lot. Set up a comfy chair and spend some time watching a sunset unfold. Sunset time and direction for your locale can be found at:

https://www.timeanddate.com/sun/

Next Week in Sky Lights ⇒ Hoar Frost

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