It is simply the result of Two different ways of describing the same sky.

L'Vedic astrology uses the sidereal zodiac, which is a system based on observation of the starry sky. However, this system Does not take the constellations as they appear in the sky with their irregular boundaries. The astrological zodiac is a symbolic and geometric division of the ecliptic: the band of sky traversed by the Sun is divided into twelve perfectly equal parts of 30 degrees each, for a total of 360 degrees.

This structure did not arise in modern times. In the traditional perspective of Vedic astrology, the twelve-sign zodiac is derived from the cosmological knowledge of the Vedas, and was later adopted and systematized even in the Mesopotamian cultures, from which the earliest historical records we know come. The Babylonians thus inherited an already structured system and used it to harmonize the movement of the heavens with the twelve-month calendar.

The key point is that in astrology the signs are not identical to the constellations (while the Naksatras are much more aligned to the constellations). The signs are twelve ideal and perfectly equal sectors, while the actual constellations in the sky have very different dimensions.

Instead, when we consult astronomical instruments such as NASA's Horizons system, we are looking at the sky according to a completely different logic. Astronomers do not divide the ecliptic into twelve equal parts, but use the actual boundaries of the constellations, officially established by the International Astronomical Union in 1930.

These constellations have irregular dimensions And they do not all occupy the same space in the sky. Some are very large, others very small. There is also a constellation along the ecliptic that traditional astrology does not use: Ophiuchus, the bearer of the snake. In NASA ephemerides it is abbreviated as “Oph.”.

If the Sun's actual path through the constellations is observed, the result is a different sequence from the astrological one. The astronomical positions of the Sun along the year thus turn out to be approximately these:

Dates of the Astronomical zodiac (Constellation Positions) of the Sun in the 13 astronomically recognized Signs/Constellations:

• Capricorn: January 20 - February 16
• Aquarius: February 16 - March 11
• Pisces: March 11 - April 18
• Aries: April 18 - May 13
• Taurus: May 13 - June 21
• Gemini: June 21 - July 20
• Cancer: July 20 - August 10
• Leo: August 10 - September 16
• Virgo: September 16 - October 30
• Libra: October 30 - November 23
• Scorpio : November 23 - November 29
• Ophiuchus: November 29 - December 17
• Sagittarius: December 17 - January 20

Here it becomes clear that the Sun passes through thirteen constellations, not twelve, and that the length of stay in each is very different. For example in the Virgin remains more than a month, while in the Scorpio only a few days.

This gave rise to the famous idea of the “thirteenth zodiac sign”. In fact, NASA has never introduced a new astrological sign. Astronomers simply describe the actual position of the Sun in front of the constellations. Astrology, on the other hand, uses a symbolic system that divides the zodiac circle into twelve equal parts.

It is therefore a matter of two different maps Of the same sky. NASA describes the sky with constellation boundaries. Astrology describes the sky with a geometric division of the zodiac mandala.

If we want to look at the issue from a broader perspective, we can say that the astronomical one is simply One of the possible ways of dividing the celestial mandala. A division into thirteen main constellations is used here.

In contrast, the Vedic tradition uses a much more harmonious and symbolic structure. The twelve zodiac signs are further divided into nine pada, or subtle parts, creating a numerical structure that leads to the number 108. In fact, twelve signs for nine pada generate 108 divisions.

Similarly, the 27 Naksatra, the lunar abodes of Vedic tradition, are divided into four pada each. Twenty-seven Naksatras for four pada still generate 108.

This number is not random. In Vedic cosmology it represents a sacred number that reflects the structure of the universe and the relationship between microcosm and macrocosm.

For this reason Vedic astrology simultaneously uses two levels of sky observation. I zodiac signs represent the geometric and symbolic structure of the zodiacal circle, they are the movement of the Sun, while the Naksatra represent an observing system much closer to the real distribution of stars and represent the movement of the Moon.

When these two levels are integrated, you get one of the most refined sky-reading systems ever developed.

One last observation may be useful for those who like to experiment directly with astronomical ephemerides. Below are the basic settings to put into Nasa's Horizon System.

If you want to use NASA data to derive the astrological position of a planet, you can do so in a very simple way. Below we see what the ephemeris table for Planet Mars looks like. In particular we can see the “Cnst” column indicating the astronomical constellation Aquarius, which might differ from the one calculated through the astrological software. But instead of dwelling on this parameter, let us take the longitude column (ObsEcLon) and derive the Vedic Zodiac Sign with a little calculation.

It is then sufficient to take this ecliptic longitude of the planet, ObsEcLon, provided by the astronomical ephemerides, and divide it into the 30-degree sectors of the zodiac. Unfortunately, these degrees are calculated using the equinox as the reference system, so the corrective factor of the Ayanāṁśa. This immediately gives the zodiac sign (+1) and the corresponding degree according to the astrological system. In this case we read, in the first row of the table, the value ObsEcLln = 340.55. Let us first remove the avanāṁśa (24.14°) and we have 316.41° (These are the sidereal degrees we are interested in). We remove multiples of 30, representing the Signs that Mars has passed from Aries, and count them. We get 11 Signs and that leaves 16.41 degrees. So Mars is in the Sign of Aquarius (11) at 16°25’.

Here is the link to the Nasa ephemerides: Horizons System

This clearly shows that there is no real contradiction between astronomy and astrology. Rather, there are Different ways of subdividing and interpreting the same sky.

Astronomy describes the position of celestial bodies in physical space. Astrology describes the symbolic structure of the cosmic mandala through which those movements are interpreted.

Two different languages applied to the same universe.