Sun constellation calculator
Which constellation contained the Sun on your birthday? Compare its IAU sky region with your tropical Sun sign, including dates when the Sun is in Ophiuchus.
Calculation method
We calculate the Sun’s geocentric apparent J2000 vector, convert it to equatorial right ascension and declination, and pass those coordinates to Astronomy Engine’s Constellation(). The routine transforms to the boundary reference frame internally. The classification follows IAU constellation regions. It identifies the Sun’s center; near a border, the solar disc can overlap two regions. This is not a visibility forecast or a sidereal-sign calculator.
Frequently asked questions
Is Ophiuchus the 13th zodiac sign?
Ophiuchus is one of the constellations crossed by the Sun’s apparent annual path. It is not a thirteenth sector in the twelve-sign tropical zodiac.
Does this change my zodiac sign?
No. This calculator answers which IAU constellation contains the Sun’s apparent center. Tropical signs are measured from the March equinox and answer a different question.
Do I need a birth time?
For most dates the constellation is unchanged throughout the day. Near a boundary, birth time and time zone determine the answer. Without a time, the calculator uses local noon and checks the start and end of the local day.