Moon, M44, and Mercury

From the photographer: “In the sky, the sickle moon was in perfect alignment with the open cluster M44 (also known as the Crib), while a little further down, bathed in the orange light of twilight, Mercury shone close to the horizon.
What made this sunset even more impressive was the presence of an intense violet light, within which the thin crescent moon was silhouetted. The phenomenon is described with great clarity by Marcel Minnaert in his famous book Light and Colour in the Outdoors, particularly on page 297, where the author explains the chromatic evolution of the sky during sunset.

According to Minnaert, violet light reaches its maximum intensity when the Sun is between -4° and -5° below the horizon, i.e. about 35 minutes after sunset. This colour band lies between the blue of the highest sky and the warm tones of the horizon ranging from salmon-red to deep orange, as illustrated in the diagram on page 295 of the same volume. Another interesting aspect is that the saturation of violet light tends to increase in the summer months, probably due to the more favourable atmospheric conditions.”

Technical details:
Canon 6dmod, Sigma 105mm, f/2, 2.5 sec, iso 100