0. A guide to the galaxy
In astrology, a birth chart is a diagram that represents the position of the planets and astrological aspects at the time of a person’s birth. These charts offer insight into what a planet's position will mean in a person's life: how their personality, wants, and needs were defined by the stars at the moment they were born.
So, if you know a date and location, you can get a birth chart. But, what if you were born under a different Sun sign? Or a different year? How would your chart change?
1. Reverse engineering the stars
Birth chart systems are quite straightforward: you input a date and location, and you get a chart containing the position of 11-14 celestial bodies and their respective traits and meanings. But there's no current way to tweak the variables. Birth charts are snapshots of a point in space and time, after all, if I were to "shift" one planet, the rest of them would "shift". Celestial bodies are in constant movement, and they have different patterns in which they do so.
The first step was understanding how celestial bodies moved and how their movement affected the others. How many hours, days, or years can one planet stay in a sign? What happens to the other planets when one of them is shifted?
Before getting into astrology, understanding astronomical behaviors was paramount. After all, the first is a range of divinatory practices based on the observation and systematization of actual celestial bodies. So, as pseudoscientific* as it is, it's based on something real. And I'm no astronomer, but I'm adept at pattern observation. So I processed years of planet transit data to come up with movement estimates and identify patterns and relations between them.
And after identifying the patterns, I classified them under an astrological lens.

*As much as I love mentioning that I'm a walking Aquarius sun stereotype, as a researcher I need to clarify that I don't believe in astrology. It's not an actual science, period. I just find the divination systems heavily complex and intriguing. Also, I adore memes and classifying people.
2. In the name of the moon, I will make a system
I had the systems, now I wanted to use them. After all, my questions were still unanswered and I was quite eager to play with hypotheticals.
How do I get a date from a given combination of signs?
How would my birth chart change if I shifted a planet?
When would a person have to be born to have their big 3 (sun, moon, rising) on the same sign?

First, I realized that it was impossible to answer my first question. Why? Because of the celestial bodies' speed.
After mapping the proportion of the moon and rising sign I realized that the closest I can get is a range of 2.5 days in which a moon sign is the same. The next fastest celestial body/planet* is Mercury, which changes approximately every 19 days.
With these times, not only it's impossible to get a precise date out of a combination of signs, it's impossible to make calculations independently. Given the different speeds and positions of the planets, there are certain combinations of birth charts that are highly unlikely or straight-up impossible.
For instance, given their similar speeds and the orbit of this planet, the Venus sign is never more than 2 signs away from the Sun sign. So you can't have someone with the Sun in Aries (sign #1) and Venus in Libra (#7).

In conclusion: planet speeds need to be considered as interconnected and dependent variables
Thus, I decided to go with a different approach: start with a birth chart, and modify the planets one by one.

* For simplicity's sake, I'm gonna refer to them as planets from now on.
3. The (solar) system
The restrictions and data are set, so the next step is building the system.
I decided to design this as a web app. Given that its main function is to play with astrological variables, at this stage I don't visualize this application as a provider of constant content (e.g. horoscopes or compatibility charts) or something that can be a strong enough incentive for people to download this into their phones or tablets. And I'm not interested in building this as a proper, scalable, and commercial product either.
This is a passion project whose purpose is to combine 3 of my biggest passions: UX design, data analysis, and astrology. Nothing more and nothing less.
Thus, considering the scope and desired functionality, this product is geared more toward expert users. Meaning, astrology enthusiasts or professional astrologers who are already familiar with birth charts. But also, the system should be clear enough to avoid being too technical/full of jargon/impossible to use without a manual. While researching, I found that most specialized astrology software is quite complex, so I wanted to avoid such a technical approach to differentiate this project from the rest.

The first thing I did was design an information architecture for the app itself. In this product, the first step is entering a date and location to generate the base chart. From this chart, the user can:
a. Change the date and location (thus, generate a new chart altogether)
b. Modify an individual planet
c. Read information related to the birth chart components

Information Architecture

For the planets, instead of designing a detailed information architecture, I chose to represent them with flowcharts.
This is because, for me, this app is process-driven. Meaning, more than thinking of specific screens, I thought it would be more useful to visualize the process itself and then choose the visual elements and design patterns that fit the process the most.​​​​​​​

Flowchart: Sun modification process

Then I designed some low-fidelity wireframes to have a general idea of the application layout. After all, more than having specific screens, this application works with processes: there are several layouts than can be repeated according to the processes each planet change requires.
Regarding branding, I chose a dark theme with a single primary hue (teal) for actionable items. It's an app about stars and mysticism, it makes sense for it to look like it's in space after all.
(And I've always wanted to design something with a dark theme 😅)
4. The Asteri universe
To get a birth chart you need a date, time, and location. So, the first thing Asteri needs to do is request this data from the user to generate the base chart.
Note: all birth charts displayed in this case study and their modifications are real and accurate. So this is a UX and data visualization project.
The birth chart is the most important component of the whole system. To design this, I analyzed several astrology and birth chart apps to select which features were the most important and how to represent them.
I decided on the following:
Then I designed the main screen and the flows to change each of the variables. For instance, this video shows the process of changing the Sun sign from Aquarius to Leo.
There are several interactions that are repeated amongst the processes. For instance:
- Selecting the new sign
- Displaying the new wheel
- Adjusting details of said wheel

I adapted these interactions to the need of each flow. For instance, changing the Rising sign doesn't modify the date, unlike the Sun. So there's no date picker in this case.
In other planets (e.g. Neptune or Pluto) ranges can span years. Thus, I believe this design approach was optimal.
I decided not to display all planets in this case study though, given how similar their UI and interactions are.
Finally, I designed the informative screens. These serve 2 purposes:
1. To educate the user about each of these astrological concepts.
2. To illustrate how these concepts apply to the active chart.​​​​​​​
5. Recap
To answer the questions in section 2:
How do I get a date from a given combination of signs?
I can't: I can only modify an existing birth chart by shifting a planet.

How would my birth chart change if I shifted a planet?
Both of the new charts displayed in the UI are modifications of mine. For instance, by changing my Aquarius Sun to a Leo, I'd have a different sign in Mercury, Venus, and Mars.

When would a person have to be born to have their big 3 (Sun, Moon, Rising) on the same sign?
The easiest way to figure this out is to start from an existing chart (your birthday or a date you're familiar with) and shift the slowest planets first.
By following this method using my birth chart as a starting point, I found out that the big 3 were in Aquarius on February 10, 1994, at 5:28 AM.

6. Following the North star
As I said before, I didn't implement this app nor do I intend to. My objectives as a designer with this project were:
1. Understand planet transit and movement patterns
2. Map the movement times and dependencies of each planet
3. Define the flows for changing each planet on the chart
4. Design a dark-themed UI to make these changes

I'd love to implement this, but manipulating NASA data and planetary charts goes far beyond my developer skills. And beyond what's fun for me (the most important factor in a personal project 😅), so there's that.

Because I'm an astrology fan, designing this product was difficult because of the curse of knowledge bias. Astrology as a practice has many specific concepts and rules. In order to design this, I had to understand these concepts and represent them in a way that could be understood clearly both by experts and relatively new users.

Furthering this, I'd love to explore the modification of the other variables of the natal chart: houses and aspects. For this project, I just left those 2 as visual and content variables related to the main ones (planets and signs). But it's also an interesting take:
Is it possible to modify a chart to get a planet and sign in a certain house?
How could this system arrange planets to be in certain angles in relation to others?

Astrology is a complex field, and Asteri barely touches the surface of it. But, as an exploration, it's quite an interesting project that manages to play with hypothetical variables in a coherent and accurate way.
Special thanks to Andrey Núñez, for tirelessly gathering and parsing birth charts with me.

Sources and references
California Institute of Technology (n.d). NASA Exoplanet Archive.
Astrolog (n.d.). Astrolog.
Astroseek (n.d). Moon Phase Calendar.
Britannica.com (n.d.) Zodiac.
Astrology.com (n.d) The Houses.
Co-star Astrology (n.d.) Houses.
Cafe Astrology (n.d.) Birth chart.
Astro App (n.d.) Astrology Software

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