Lesson 6 of 6
Assemble your chart.
At the beginning, we imagined standing beneath a birth sky. Now we can bring the directions of the planets and the view from Mira’s birthplace together on one page.
Mira’s birth record gave us a starting point: London, 1 January 2000, at 12:00 UTC, with the rounded coordinates 51.5° north, 0.12° west. We have since learned how to measure a direction around the zodiac, find the planets at that moment, and relate the circle to her local horizon. The houses give us a further way to divide that circle. We are ready to bring those results into a completed chart.
As you read the wheel below, look for the connections we have built across the lessons. The outer ring names the zodiac signs, so a planetary marker’s direction leads you to its sign and degree. The Ascendant anchors the left-hand side of the wheel, while the numbered divisions show the houses. Each part has its own role, but all of them meet on the same circle.
Carry the birth record into the chart.
Before we calculate Mira’s chart, we check that her birth moment is expressed in UTC and that her coordinates keep their direction signs: +51.5 for north and −0.12 for west. We also choose how to divide the houses. Equal houses make a useful starting point because we can reconstruct their boundaries ourselves, beginning at the Ascendant and moving another 30° for each cusp.
The zodiac needs its reference too. We will use the Fagan–Bradley sidereal zodiac introduced earlier, with its date-dependent offset from the tropical reference. Keeping the birth moment, location, zodiac reference and house system beside the result makes it possible to understand a difference between two charts. Even when both carry the same birth date, a different time or convention can change what appears on the wheel.
Bring the calculated directions onto the wheel.
For Mira’s birth instant, the calculation evaluates the prepared planetary curves we explored in lesson three. Her birth time and place also let it find the local angles from Earth’s orientation. It applies the date’s ayanamsa to express the longitudes in the Fagan–Bradley sidereal zodiac, then constructs the selected houses in that same reference. We can therefore read the planetary markers, chart angles and house cusps together.
The drawing places these numerical results around the wheel. A marker’s direction from the centre represents its longitude, just as it did on our simpler zodiac circle. You may notice that some labels sit farther from the centre than others so they can fit without overlapping. That spacing helps us read the drawing; it does not show a planet’s distance from Earth.
The wheel shows the Sun, Moon, the planets from Mercury through Neptune, and Pluto. When several markers sit close together, the result tables give you room to read their exact positions. Those tables also include Ceres, Chiron, the lunar nodes, and the four chart angles, so the drawing and the tables offer two ways to examine the calculation.
Use Mira’s record in the calculator below, or carry forward your own prepared birth details. Begin with Equal houses if you want to check the boundaries using the method we worked through in the previous lesson.
Your sky, calculated
2000-01-01 at 12:00 UTC · 51.5° latitude, -0.12° longitude
Change birth details
Your turn
Choose your moment.
Use your own birth details, or follow Mira. Enter the date and time in UTC, including any change of date when converting from local time.
2000-01-01 at 12:00 UTC · 51.5° latitude, -0.12° longitude
Saved birth details stay in this browser when you reload or return. Use Mira’s example to clear your saved record. No birth details are sent anywhere. Planet calculations arrive in a later lesson.
Each calculation loads only the sky data needed for your birth year, usually less than 100 KB, alongside the calculator. Saved birth details stay in this browser for your next visit.
Read back what you built.
Start with the Ascendant, which should appear on the left of this wheel. Its sign need not be Aries: the drawing turns the zodiac circle to put the rising point at the left, while keeping all the positions in their proper relationship. Follow the circle halfway around to find its opposite, the Descendant. You are locating the two ends of the horizon we introduced in lesson four.
Now choose a planetary position in the table and trace it to the sign on the rim. The table gives you a precise number, while the wheel lets you see its place among the other directions. To connect the two, we can use the same small calculation we practised in lesson two:
17° Taurus = 30° + 17° = 47°
Taurus begins 30° along from the zodiac’s zero point. Adding the 17° within Taurus gives a longitude of 47°. This is a reading example, rather than a claim about one of Mira’s calculated planets; you can follow the same steps with a position from her table.
Finally, check the house boundaries against your chosen method. For Equal houses, each cusp is another 30° along from the Ascendant. For Whole Sign houses, the first house begins at the start of the Ascendant’s sidereal sign. If you requested Placidus, read the method label as well: it tells you whether the calculation used Porphyry instead. That label belongs to the result because a different method means different boundaries.
Explore what a change can tell you.
We can now return to the birth record and change one detail at a time. Try changing the time, then compare the angles and house boundaries with the earlier result. Keeping the other inputs fixed lets you connect the difference to the single change you made, rather than trying to explain several changes at once.
This is also useful when a birth time is approximate. Exploring nearby times shows how the chart responds to that uncertainty, especially in its angles. The calculation can return a precise-looking number for each trial, but those digits cannot make an uncertain birth record more precise. Keep the quality of the record in mind as you read the result.
For curious programmers: carrying the same journey into an application
Using the library in your own application follows the journey we have completed here. Load prepared ephemeris data, supply an unambiguous instant and location, choose the houses, and request the sidereal result. Reuse the data when someone changes the birth details, so the application does not have to load it again for every calculation.
The Rust runtime accepts an Ephemeris and a ChartInput. The input carries an Epoch, Location, and HouseSystem. This course’s browser adapter calls the sidereal entry point and turns its returned positions into the tables and wheel above.
Keep loading and display in the application. That lets the same calculation serve a browser or a Worker. The app README documents the adapter and reproducible build; the lessons above explain what those calls mean.
Make it yours
Try the idea.
A few questions to put the pieces together. Take your time; you can try again.
A sky you can reconstruct.
We began with a birth record and a question about the sky. Following Mira’s example has shown us how that record becomes a chart: UTC and coordinates identify the moment and place, an ephemeris provides planetary positions, and the sidereal reference lets us express their directions as signs and degrees. The local horizon establishes the chart angles, and our chosen house method divides the circle around them.
When you return to Mira or try another birth, you can follow those connections again. Choose a position, an angle or a cusp and ask which step put it there. The finished chart gathers the answers into one picture, and you now have a way to work back through the calculations behind it.