About

The Ascendant (or Rising Sign) is the zodiac sign that was ascending on the eastern horizon at the exact moment of your birth. Unlike your Sun sign, which represents your core ego, the Rising sign represents your social mask, physical appearance, and first impressions. It is the "cover of your book".

Calculating the Ascendant requires high-precision astronomical data. Because the Earth rotates on its axis every 24 hours, the Rising sign changes approximately every two hours. A difference of just 4 minutes in birth time can shift the degree by ~1°, potentially changing the entire sign.

This tool uses the Swiss Ephemeris mathematical approximations to calculate the Local Sidereal Time (LST) and the oblique intersection of the ecliptic with the horizon for your specific latitude and longitude.

Formulas

The calculation of the Ascendant involves solving the spherical triangle formed by the intersection of the ecliptic, the celestial equator, and the local horizon. The core formula derives the angle ASC from the Local Sidereal Time (LST), the Obliquity of the Ecliptic (ε), and the observer's Latitude (φ).

ASC = arctan2cos(LST)−sin(LST) × cos(ε) − tan(φ) × sin(ε)

Where LST is calculated from Greenwich Mean Sidereal Time (GMST) and Longitude (λ):

LST = GMST + λ15

Reference Data

Element	Symbol	Meaning	Value Range
Julian Date	JD	Continuous count of days since 4713 BC	2400000+
Obliquity	ε	Tilt of Earth's axis relative to ecliptic	~23.44°
Sidereal Time	LST	Time measured by stars, not sun	0h - 24h
Ascendant	ASC	Intersection of Ecliptic & Horizon	0° - 360°
Right Ascension	α	Angular distance along celestial equator	0h - 24h
Declination	δ	Angular distance north/south of equator	-90° to +90°
Latitude	φ	Observer's geographic latitude	-90° to +90°

Frequently Asked Questions

The Ascendant moves 1 degree every 4 minutes. A 15-minute error can shift the Ascendant by nearly 4 degrees, which might push it into the next zodiac sign, completely altering the interpretation.

Your Sun Sign represents your core identity, ego, and life purpose. Your Rising Sign (Ascendant) represents your demeanor, physical body, and the lens through which you view the world. It is the "First House" of your chart.

Since DST rules vary historically and geographically, we ask you to specify the Timezone Offset or check the DST box. In our City Search, we provide the standard offset, but you must confirm if DST was active on your specific birth date.

Yes. The algorithms account for negative latitudes. Note that in the Southern Hemisphere, the signs may appear "inverted" relative to the compass directions compared to the North, but the zodiacal calculation remains astronomically correct.