PRACTICE / 25 OF 36
Build Your First Chart
By the end your own chart is set up in this app, and you know what each field you filled in actually changes.
Approved original lessons, free on the web · 2026-10-12
THE IDEA
Task: set up your own chart and find out what each field changes.
Diagram: a double ring. The outer ring is divided into twelve parts for the signs, the inner ring stands for the houses, and a horizontal line on the left is labelled ASC, the starting point. A concept figure with no real degrees.
Date, time, place and time zone each change your chart.
What the four fields do
The date fixes which sign the Sun and most planets are in. The time fixes the Ascendant, the Midheaven and the twelve houses; fill it in and that layer appears. The place plus the time zone fix what the clock said where you were at that moment.
How this tool worksOne time zone out moves the whole chart an hour earlier or later. So a wrong time zone matters as much as a wrong birth time.
Derived calculationThis app’s city search brings the time zone with it, which is safer than typing one in yourself.
How this tool worksWhat the old texts say: in Book III ch. 2 of the Tetrabiblos, Ptolemy takes the degree rising on the eastern horizon at the moment of birth as the chart’s starting point, so both the moment and the place are needed.
Cited sourceOnce the chart is set up, check your typing, the blanks and the candidates, then start reading.
Three checks once it is set up
Once the chart exists, check three things. First, go back over the date, time and place you typed. Second, look at the Ascendant row. Third, see whether any body is marked “unconfirmed” with two candidates.
Reflection promptIf you entered no time, the Ascendant row stays empty, which is exactly the correct result. A body marked “unconfirmed” changed sign on the day you were born. You can edit your data in settings at any time, and the whole chart is worked out again.
How this tool worksThe two most common typing slips are mixing up morning and afternoon (2:30 and 14:30 are twelve hours apart) and swapping month and day (4 March entered as 3 April). With those three checked, your chart is solid material to work with.
Reflection promptOBSERVE YOUR OWN CHART
Look at my chart
Now actually do it: set up or check your own chart.
- In settings, confirm your birth date, time, place and time zone.
- Back on the chart page, check the Ascendant row: filled if it should be, empty if it should be.
- Note which bodies are marked “unconfirmed”; later lessons use this.
Without a birth time, rising sign and houses stay blank.
LOOK CLOSER
A common mix-up
“The time zone hardly matters — it is the same day either way.”
One zone out is an hour out. The Ascendant changes sign roughly every two hours, and the whole set of houses moves with it.
“An empty Ascendant row means the app is broken.”
With no birth time, empty is the correct result; once you add a time, the Ascendant and houses appear.
CHECK YOURSELF
Now, try it yourself.
Sources and rights
- Ptolemy, Tetrabiblos, trans. F. E. Robbins (Loeb Classical Library, 1940)
Book III ch. 2 takes the degree rising on the eastern horizon at the moment of birth as the chart's starting point, so the moment and place are required. The breakdown of what each field affects is this lesson's arrangement, and the city search carrying the time zone is this app's behaviour.
The Robbins translation is in the public domain, as the University of Chicago LacusCurtius copyright page records. The transcriber's own notes and layout are not cited. · 2026-10-10
Limits of this lesson
Without a birth time the Ascendant, Midheaven and houses stay empty until you add a time.
The name is not used in any calculation, and you do not type the time zone yourself.
The demonstration data is not a real person and not a model answer.
YOUR STUDY
Write what you learned in your own words.
Write it down: which piece of your data were you least sure of, and how did you check it?
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