Zodiacal Position¶

When we calculated the current position of the Sun, pyswisseph output the body’s ecliptic longitude from Earth’s point of view—in our example, 196.1388645301424 decimal degrees (DD). This absolute longitude is measured counter-clockwise along the ecliptic plane, starting from the vernal equinox.

The 12 signs of the zodiac are 30-degree segments of this 360-degree circle. Each segment is an “alias” for a specific longitude range. The tropical zodiac places 0 Aries at the vernal equinox (0.0 DD), while the sidereal zodiac uses an offset (ayanamsa) that may reference fixed stars.

Tropically, the starting absolute longitude of each sign is:

Thus, 196.1388645301424 DD is a complete position if you only need absolute coordinates. However, to translate this to the more common degrees-minutes-seconds (DMS) format relative to the sign (where the degrees reset to 0 at the cusp of each sign), pyswisseph provides the function swe.split_deg() that takes DD positions and flag constants. The flags tell the function how to split the degree value.

We will use swe.SPLIT_DEG_ZODIACAL, which tells the function to reset the degrees at the start of each sign and append the sign’s index to the result.

Ecliptic longitude DD -> sign DMS¶

Let’s take our Sun position and translate it to zodiacal position and DMS.

import swisseph as swe
from datetime import datetime, timezone

# 1. Get current time in Coordinated Universal Time (UTC)
now = datetime.now(timezone.utc)

# 2. Convert from UTC to Julian Day (JD) in Terrestrial Time (TT).
# 'jd_tt' is the second element (index 1) of the returned tuple.
jd_ut, jd_tt = swe.utc_to_jd(
    now.year,
    now.month,
    now.day,
    now.hour,
    now.minute,
    now.second + now.microsecond / 1000000.0
)

# 3. Calculate Sun position (swe.SUN is the constant for the Sun)
# We use `jd_tt` for accurate planetary positions.
coords, flags = swe.calc_ut(jd_tt, swe.SUN)

# 4. Extract longitude (first element of the 6-element coordinates tuple)
longitude = coords[0]

# 5. Split longitude into degrees and signs
dms = swe.split_deg(longitude, swe.SPLIT_DEG_ZODIACAL)

# 6. Index the signs
sign_order = (
            "Ari", "Tau", "Gem", "Can",
            "Leo", "Vir", "Lib", "Sco",
            "Sag", "Cap", "Aqu", "Pis"
            )

# 7. Get sign name from index
sign_name = sign_order[dms[4]]

# 8. Format output
print(f"{dms[0]} {sign_name} {dms[1]} {dms[2]}")

# Example output:
# 16 Lib 38 15

Understanding the swe.split_deg() output¶

The swe.split_deg() function, when called with the swe.SPLIT_DEG_ZODIACAL flag, returns a 5-element tuple containing the 0-based zodiacal position:

The sign index at dms[4] corresponds to the 0-based array/tuple index:

• 0: Aries

• 1: Taurus

• 2: Gemini

• 3: Cancer

• 4: Leo

• 5: Virgo

• 6: Libra

• 7: Scorpio

• 8: Sagittarius

• 9: Capricorn

• 10: Aquarius

• 11: Pisces

By using this index to access the sign_order tuple, we successfully translated the raw output into the human-readable string: 16 Lib 38 15.