Your Astrology Birth Chart

The first, and most important thing you must have when casting your astrological birth chart is accurate birth data. This includes your birth date, birth time, and birth location. While this information doesn't need to be absolutely exact to be useful, the more precise your birth data is the better.

The best source for accurate birth data is from your birth certificate. If you do not have your birth certificate then you can cast a chart from a general time based on memory, and hopefully find ways to rectify the time based on what you know to be true in your own life as it is reflected in the chart.

This page talks about the different types of birth charts, how to calculate them, and the planets used. To see how to begin reading a natal chart, please see my page on Birth Chart Analysis.

Movement of the Planets Through the Zodiac

Depending on how deep you want to dig into the details of your birth chart will determine how exact your birth data needs to be. For instance, if you want to know your Sun Sign, then you will need to be within a 30 day range because that is how long it takes for the Sun to go through each Zodiac Sign. If you want to know your Moon Sign, you would need to be within a 2.5 day range of accuracy, because that is how long it takes the Moon to go through each sign. If you want to know your Rising Sign you would need to be in a two hour range, because that is how quickly each sign rises over the Eastern horizon.

On this site, I primarily focus on locational astrology, which requires that your birth data needs to be even more exact than that, almost down to the minute to give the most proper results. This is because the lines on the astrology map move so quickly in relation to the Earth's spin, as well as each planet following its own orbit around the Sun, that the astrological influences can shift from one location on the map to another within the span of a few minutes. These influences can be so stark, that if they are projected onto an astrology map, in a location that isn't accurate, then you would be doing yourself a disservice by potentially moving to a location that would give you unnecessarily difficult results!

This is because the Earth is spinning on its axis so fast, while simultaneously spinning around the Sun, along with the other planetary bodies moving along their own orbits, that as the more time lapses the further these astrology map lines shift from their actual placements of influence as they relate to your life.

Different Zodiacs and House Systems

Before I dive into this topic I want to point out that there are a lot of strong opinions about what the correct and incorrect zodiac and house systems to use are. My take is that they are all correct if you know how to read them! So keep an open mind and use what works for you.

Tropical Zodiac and Placidus House System

Once you input your birth data there is a myriad of different settings on how you want to calculate your birth chart in order to read what the planets are doing. In modern Western Astrology the most common settings used are the Tropical Zodiac with the Placidus House System.

The Tropical Zodiac is easy to calculate because the Sun Signs follow the seasons, where each year on the first day of Spring in the Northern Hemisphere the Sun goes into Aries on March 21st. Aries is the first sign in the zodiac, so every thirty days, give or take, the Sun changes signs, through the zodiac following the seasons, until it returns to Aries the following year when Spring rolls around again.

The Placidus House System shifts greatly depending on latitude. The further you are north or south of the Equator the more the degrees will shift between the different house calculations. The Placidus House System seems to work well with the Tropical Zodiac in that they both are very psychological in nature, and since this is the most common calculation in Western Astrology, if you know your Sun Sign, Moon Sign, and Rising Sign in this manner, there is universal understanding of how they can be interpreted.

To determine planet strength in this way you would look at aspects as they are calculated by degrees and orbs. For instance, Sextiles are 60 degree aspects, Squares are 90 degree aspects, Trines are 120 degree aspects. If planets and angles form aspects to one another based on these degrees then they are influenced by one another based on their planetary significations. The strength of these aspects depends on how tightly the degrees are, this is called the orb, usually orbs are considered within a 5 degree range.

Sidereal Zodiac and Whole Sign Houses

Because I come a Vedic Astrology background, my default calculations when looking at the natal chart are with the Sidereal Zodiac and Whole Sign Houses, which is the primary way it is calculated in Indian Astrology.

To calculate the Sidereal Zodiac you need to determine a fixed star for the signs to start each year, which varies ever so slightly from the seasonal dates that the Tropical Zodiac is tied to. The Sidereal year is slightly shorter, which means the Sidereal Zodiac moves further behind the Tropical Zodiac one degree every 72 years. The two zodiacs were exactly aligned around 2,000 years ago, but have now deviated to around 24 degrees away from one another, at this point in time, and will continue to deviate further as the years and decades roll on.

There are multiple ways to calculate your birth chart in Sidereal format based on what fixed star you choose, this is called the Ayanamsa. The Lahiri Ayanamsa is the most common calculation used in Vedic Astrology, and is tied to the fixed star, Spica. I use the True Chitrapaksha Ayanamsa, which also uses the star Spica, but the calculation is slightly different from Lahiri as it takes into account the slight movement of the star for a more accurate calculation of it's true location in the sky.

Whole Sign Houses connect each sign with a house, starting with the 1st House as the sign that is rising over the Ascendant. In Vedic astrology, the Rising Sign becomes the most important starting point when analyzing a birth chart because the 1st House represents your self and identity, and as a whole sign house this can be established as a sign in the zodiac, in relation to the other signs, dependent on which house they fall in.

To determine planet strength in this way, we would first determine which sign the planet is in, whether it is exalted, debilitated, own sign, friend, or enemy. Then we would see which planets are giving and receiving aspects based on how that planet behaves. For instance, Mars aspects 4th and 8th from (Square), Saturn aspects 3rd and 10th from (Sextile), Jupiter and Rāhu aspect 5th and 9th from (Trine), and all planets aspect the sign opposite from them.

Outer Planets

Traditional Vedic Astrology does not take into consideration the three outer planets, Uranus, Neptune, and Pluto, because this branch of astrology was practiced long before these planets were discovered. Vedic astrology uses nine planetary bodies, including Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Rāhu (North Node), and Ketu (South Node).

I find that this is plenty sufficient when analyzing a natal chart because so many rules and techniques have been developed within this branch of astrology that personality traits and planet strength can easily be determined.

When it comes to the practice of locational astrology, however, I absolutely take into consideration the three outer planets, as well as two astroids, Chiron and Ceres. This is because Astrocartography is a relatively new practice, and these additional planetary bodies definitely have influence when looking at the finer details of these energies coming together, especially when considered in connection with the map of the world, and the great many places in the world you could choose to be.

Related Pages

Birth Chart Analysis

A thorough birth chart analysis is important in determining how the range of possible planetary influences will manifest in your life, and on your astrology map.

Locational Astrology

Locational astrology is total make up of all planetary influences in a geographic location, including planet strength, astromap, relocation charts, and timing.

Astrology House Meanings

The houses in astrology represent different areas of life, learn the twelve astrology house meanings and how the planets manifest their energy through each.