Ascendant and Descendant
The current ascending and descending point of the celestial circle.
The Ascendant marks a direction on the eastern horizon that shows the rising point of the celestial circle, the apparent path of the sun (the ecliptic) at a given time. It also marks the sign that is about to rise.
The sky apparently rotates within 24 hours, which means that the Ascendant moves one degree every 4 minutes. This is why it is crucial to use the most accurate time of birth possible. The Ascendant is the fastest point that moves in the sky and therefore the most personal element in the birth chart.
The Ascendant is the starting point of the astrological houses, the 12 houses of the birth chart.
Opposite we find the Descendant, the current point on the western horizon where the sun descended, the peak of the Seventh House of the birth chart.
The Ascendant/Descendant line comprises the horizontal axis of the birth chart and is based on specific astronomical calculations.