Astronomical twilight

{
  "id": "MLC-T-MET-003655",
  "term": "Astronomical twilight",
  "field": "Meteorology and atmospheric science",
  "definition": "The period of twilight that begins or ends when the Sun's center is 18 degrees below the horizon. During this time, the sky is completely dark for most purposes, and only the faintest stars and celestial objects are visible. It marks the transition between night and the brighter phases of twilight, such as nautical and civil twilight.",
  "see_also": [
    "civil twilight"
  ],
  "url": "https://mlchart.com/terminology/meteorology/astronomical-twilight/"
}