Almost accurate birth charts

The ancients strove to make sense of the world just like we do and in their search for understanding they focused their gaze on the stars in the sky.

They gathered astrological knowledge, but it’s unknown if these ancient astrologers had calendars, clocks and atlases or if they understood the technicalities of chart calculation.

Their astrological legacy includes birthcharts, progressed aspects and authentic astrological information and thanks to Ptolemy, and the stars in the sky, humanity can now benefit from their astrological wisdom.


The fundamental astrological text that became the standard reference for all astrologers during the Age of Pisces was Tetrabiblos.

It was written by Claudius Ptolemy in the 2nd-century.

Working in the library at Alexandria – where an estimated 700,000 papyrus rolls were carefully catalogued – he summarized the astrology of the ancients.

His famous text is an exposition of the art of astrology and a compendium of astrological law.

In it he systematically explains the rules for drawing up a chart.

The planets, he claims, exert their influence on the personality as do race, country and upbringing and the birth chart should be constructed for the precise moment of birth.

But the precise time is difficult to know without a reliable clock and there wasn’t one in the 2nd-century when Ptolemy wrote Tetrabiblos.

What’s the date?

A calendar divides the year into months, weeks and days.

It’s a method of ordering the years – an essential part of the astrology story.

Way back….the Sumerian calendar divided the year into 12 lunar months of 29 or 30 days and today the Jews, Chinese and Muslims have calendars based on lunar and solar cycles, each with a different starting date.

But it doesn’t matter where you are you just want to know what day it is.

In 46BC the Julian calendar was invented by Julius Caesar, but it had an in-built error and in 1582 Pope Gregory eliminated the error and avoided its recurrence by restricting century leap years to those divisible by 400.

The changeover to the Gregorian calendar was gradual and England didn’t make the change till September 2, 1752 when the error amounted to 11 days.

That’s when September 3, 1752 became September 14 and births before and after this date were referenced as Old Style or New Style.

Germany had already made the change in 1700 but Russia didn’t make the change till February 14, 1918.

This calendar is the one you use today, unless you live in China.

What’s the time?

Clocks time the hour and minute of the day, but the common wristwatch is a quite recent invention.

Back in the 2nd-century when Ptolemy was writing Tetrabiblos there were water clocks, candle clocks, sundials and hour glasses.

They weren’t very reliable – there was no hour or minute hand – but back then the need to know the time wasn’t a five-minute imperative like it is today. This seems to be a recent cultural phenomenon.

So fast forward to the 1500s when early timepieces only had an hour hand.

Their accuracy was so poor that they were practically useless.

Then, in 1657 a great leap forward occurred when Christiaan Huygens, a Dutch physicist, made a successful pendulum clock and in 1675 Huygens devised the spiral balance spring.

This paved the way for increased accuracy – from perhaps hours per day to 10 minutes per day.

Pocket watches now had a minute hand, but most people didn’t have one – they were costly symbols of a person’s wealth and social standing and this meant that only the rich were likely to own one.

In the 1700s mechanical timekeepers – clocks and pocket watches - were uncommon.

Then in 1854 the Waltham Watch Company in Massachusetts pioneered the mass production of watches.

In 1900 wristwatches were mostly worn by women and in 1969 the introduction of the quartz watch was a revolutionary improvement in watch technology.

It made the precise timing of births – to the exact second – possible.

Ptolemy is looking on with envy.

Where are you?

An atlas is a book of maps and the zero-degree line of latitude was determined by Ptolemy as early as 150AD.

He explained it in his famous atlas, Geography – his impressive attempt to map the known world giving the latitude and longitude coordinates of major places. And even though the coordinates were hopelessly inaccurate it was a standard source of geographical data until the 16th-century.

The first modern atlas was completed in 1594, but its accuracy standard was still very poor.

The zero-degree line of longitude doesn’t have an obvious starting point – like the equator – so English navigators in the 1700s used the longitude of their home port, Greenwich.

Then in 1759 John Harrison perfected his marine chronometer and this paved the way for accurate longitude measurements and accurate map making and accurate latitude and longitude coordinates were just what the astrologer needed.

Pisces and the age of inaccurate birth charts

But, by all accounts, astrologers during the Age of Pisces applied Ptolemy’s astrology to inaccurate birthcharts.

It begs the question – how could William Lilly, Elias Ashmole, Nicholas Culpepper and John Dee get it right when the clocks and atlases were wrong?

Uranus was discovered in 1781, Neptune was located in 1846 and Pluto was discovered in 1930 so they mostly worked with seven planets and it was not until 1795 that a listing of the planets’ sign positions appeared for the first time in Raphael’s Ephemeris.

And who knew what house system to use?

The Italian astrologer, Placidus de Titus, had published his Table of Houses in 1650, but it wasn’t translated into English until 1814.

The calculation of an accurate birth chart requires an accurate birth time and accurate birth place coordinates.

It involves a difficult set of calculations that very few so-called astrologers during the Age of Pisces could understand and do.

Is it any wonder that the chart was used as a divinatory device?

An almost accurate birth chart

Now in the Age of Aquarius there’s been a revolutionary change.

The computing power of new-age technology calculates an almost accurate birth chart in seconds.

And with an almost accurate birth time recorded on your birth certificate it’s a best case scenario.

An almost accurate birth chart and evidence-based scientific astrological data allows you to live an examined life.

Author: DW Sutton

Astrology for Aquarius – sharing our knowledge

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