Classify the astronomical twilight band from the solar altitude.
Solar altitude above the horizon, degrees.
The TwilightPhase: 'day' (≥6°), 'golden' (−0.833°..6°), 'civil' (−6°..−0.833°), 'nautical' (−12°..−6°), 'astronomical' (−18°..−12°), else 'night'.
'day'
'golden'
'civil'
'nautical'
'astronomical'
'night'
Classify the astronomical twilight band from the solar altitude.