Archive for the ‘Time’ Category

Astronomical Twilight

The period after sunset when the sun has dropped between 12 and 18 degrees below the horizon.

It is the final phase of twilight, the other two phases being civil twilight (sunset to 6 degrees below the horizon) and nautical twilight (sun is between 6 and 12 degrees below the horizon).


The maximum altitude of a celestial body above the horizon. In other words, when an astronomical body transits the meridian.

Draconic Month

The time that passes between successive passes of the Moon through its ascending node. Its average value is 27.21222 days.


Literally, equinox means “equal night”.

In other words, at the Spring (Vernal equinox) or Autumn (Autumnal equinox) the daylight hours are equal to the darkness hours i.e 12 hours each. Technically speaking, the equinox is the point at which the ecliptic and celestial equator intersect.

The Big Bang Theory

The theory that the universe came into existence at one set moment in time. It has gradually come to be accepted as being correct.

Switch to our mobile site