However, our sun's disc occupies about 32 arc min in our sky. I define sunrise and sunset times to be those at which our sun comes in or goes out of view. At low and middle latitudes, atmospheric refarction increases day length by 5-10 min, but by much more at higher latitudes, at which location our sun's apparent position remains very close to the horizon for greater time periods. Solar energy is greatly scattered and absorbed, even by a 'clear' atmosphere. Thus, colors toward the blue end of the visible spectrum are preferentially scattered, and our sky appears blue.
Aerosols scatter proportional solar energy to frequency.
They also scatter more toward the blue end of the visible spectrum, but also significant amounts in other colors. Clouds scatter solar energy fairly equally in all frequencies, and thus appear whitish. Thier bases often appear dark beacuse very little solar energy is reflected up toward them and scttered back toward ground. That is small compared to some other inaccuracies. It is fine with me if you do so, so long as you mention that I made a few suggestions.