Create Your First Chart with the Chart Tool

Now it is time to try the tools. A quick way to learn astrology is to create your own chart and explore it: you have a reason to understand this particular chart. Open Chart at the top of astro.how and follow along. In about five minutes, you can have your first natal chart.

Three details to prepare

A natal chart shows celestial positions at your birth as viewed from your birthplace. You need three details:

• Birth date: Year, month, and day establish approximate Sun and planetary signs.
• Birth time: Hour and minute. This is crucial and often overlooked; we will explain why below.
• Birthplace: A city is enough; the system converts it to coordinates. Together with time, this establishes the horizon and your Ascendant.

In Chart, select Natal chart as the chart type. Give it a Chart Name, such as “Me,” enter Birth Location and Birth Date and Time, then select Show Chart. The AI conversation sits beside the chart. To keep it, sign in and select Save below it. Later, find it under My → My Charts at the top right.

You can see location’s effect directly: if Chen Yutong were born in London or New York at the same instant, the Moon and planetary signs and degrees would be identical. The horizon would differ, changing the Ascendant, Midheaven, and houses together.

Why birth time matters so much

Ten or fifteen minutes can matter. Earth’s rotation makes the sky appear to turn once per day, or about one degree every four minutes. A ten-minute birth-time difference may shift the Ascendant by two or three degrees; an hour may move it into the next sign.

When the Ascendant moves, the whole house system rotates. Your Sun could move from the 10th house to the 9th, or Venus from the 7th house to the 6th, substantially changing an interpretation.

Experiment with fictional Chen Yutong’s chart (September 12, 1992, 22:30, Taipei). Drag the time to see what changes if she were born earlier or later. On the left is Taipei’s sky at that instant: the horizon stays fixed while the ecliptic, Sun, and Moon turn. The ecliptic’s intersection with the eastern horizon is the Ascendant. The chart always places it on the left, so the zodiac and planets rotate together and planets change houses. Their sign positions barely change. An hour earlier, the Ascendant retreats from Gemini to Taurus and the Sun moves from the 4th to the 5th house. Ninety minutes later, the Ascendant enters Cancer and the Sun moves to the 3rd house. Across six hours, however, the Moon moves only from 24° to 27° Pisces; other planets barely move.

So:

If uncertain, use noon as a placeholder and remember that planetary signs may be useful while houses are uncertain. Refining an unknown time is the advanced technique of birth-time rectification, outside this introductory course. For now, calculate the chart and learn to read it. The astronomy behind birth time appears later in Basic Astronomy.

Change the time on a sample chart set to noon because the birth time is unknown. Observe what changes and what remains usable:

Meet the chart you have drawn

At first, the chart may look like a circle packed with symbols. Use fictional Chen Yutong’s natal chart below as a reference. Start by recognizing three structural layers:

The outer ring is the zodiac wheel. It has twelve equal sections from Aries through Pisces: the zodiac signs. It is a fixed ruler showing the sign and degree of each position.

The inner sectors are the twelve houses. Lines radiating from the center divide twelve life areas: self, money, communication, home, and more. Their sizes need not be equal; this depends on house system and birth latitude. astro.how uses the common Placidus system. See Introduction to the Twelve Houses for their meanings.

See why widths differ on the celestial sphere: the thick line marks the ecliptic from the Midheaven to the Ascendant (houses 10–12), which Placidus divides into three parts by time. Drag the time or switch to higher-latitude London to see larger differences in house widths:

The symbols scattered around the chart are planets. Each sits at its zodiac degree, showing its sign and house at a glance. Colored lines between planets are aspects.

Read the degrees rather than estimating

A glance can mislead when a planet sits near a sign or house boundary. On astro.how, hover over a planetary symbol to read its sign, degree, and minute. Hover over a house sector to read its cusp, or starting degree. Tap on a phone for the same information.

Compare degrees to determine houses: a planet past one house cusp but before the next belongs to that house. The chart below deliberately includes points near boundaries. Read them precisely:

Find your anchor: the Ascendant

Identify the Ascendant (ASC) first. It sits around nine o’clock on the left of the wheel, marking the zodiac degree rising on the eastern horizon at birth and the start of the 1st house.

The Ascendant anchors the chart: count houses counterclockwise from it. It also represents first impressions and how you approach the world. Your rising sign is the sign containing this point. Read The Ascendant for more. Finding it gives you a reliable orientation.

How sensitive is it? Move the previous chart’s birth time two hours later:

Make more charts to develop familiarity

The chart tool gives immediate results. Try charts for family, close friends, or public figures you like. Ask, “Where is this person’s Sun? Does their rising sign resemble my impression of them?” Comparing examples can build familiarity faster than memorizing definitions.

If a symbol or line is unfamiliar, ask the AI beside the chart. Recognizing the chart’s vocabulary helps you ask precisely. The next four lessons introduce signs, planets, houses, and aspects before focusing on AI questions.

You now have your first chart and recognize its structure. Next, explore the outer wheel in A Quick Tour of the Twelve Signs and learn each sign’s energy style.