There exists a specific time interval, where the sun’s position lies a mere 6 degrees beneath the horizon, this occurs during both dawn and dusk. During this phase, the horizon line is typically clear-cut, with the most luminous stars discernible considering ideal atmospheric circumstances, such as the absence of moonlight or other sources of intense reflection. It’s worth noting that ordinary outdoor pursuits can be carried out, as there’s still enough shading for visual comfort and security.
The period continues, where the sun descends further and finds itself positioned between 6 and 12 degrees below the horizon. This can be witness during both dawn and dusk as well. The silhouette of the horizon stays sharply defined and you may discern the shapes of certain objects even without the support of man-made lighting. However, without additional illumination, partaking in usual outdoor ventures becomes a challenge.
Following this, there comes a phase when the sun is between 12 and 18 degrees beneath the horizon, either at sunrise or sunset. Note that during this juncture, the sun’s light no longer contributes to lighting up the sky, either before this point in the early hours, or after this period in the twilight. At the dawn of what astronomers refer to as ‘astronomical twilight’ and its conclusion during the evening, the sky becomes an expanse of very faint light, possibly imperceptible.
The duration that gets sandwiched between the Civil Sunset and Civil Sunrise is a period to note. A similar observation can be made about the time span which is defined by the instance of Actual Sunset and the point of Actual Sunrise.