The Ascendant

The Ascendant or rising sun, is the zodiacal sign and degree that was ascending on the eastern horizon at the specific time and location of an event. If, for instance, this degree happens to be in the Cancer section of the zodiac, the newborn individual is known to be "Ascendant Cancer". Another individual may be "Ascendant Leo", "Ascendant Sagittarius", or "Ascendant Capricorn", and so on.
Therefore, it's the moment of the day when one is born that determines one's Ascendant.
The nuances brought by the Ascendant to the general characteristics of the sun Sign are by no means negligible. The Ascendant modifies and particularizes the sun Sign. For instance, a Sagittarius individual with the Ascendant in Aries is not the same personality as another a Sagittarius individual but with the Ascendant in Pisces . The former will be inclined by the Ascendant Aries toward dynamism, heroism, and confrontation, whereas the latter will be inclined by the Ascendant Pisces toward more ponderation, moderation, and reverie.