Sun, Moon and rising: your big three

Western astrology · tropical zodiac · Updated 2026-10-07

Your big three are your Sun sign, your Moon sign and your rising sign, which is also called the Ascendant. The Sun sign comes from your birthday, and on just over half of all days so does the Moon sign. The rising sign needs your birth time and place.

Cast your chart

Finding all three in OMNIA

Open OMNIA and tap the brass astrolabe labelled “Western Astrology”. There is no start button. The form only appears after that tap.
Fill in your birth date, time and place, pick one of the six areas under Domain of Inquiry, and press the seal marked Commence.
Below the wheel, under a small line of chart details, the line that starts with ASC gives your rising sign. The Sun and the Moon are in the planet list under it, each with its sign and degree.

Degrees are given to two decimal places, 15.37° for example, which is about 15°22′ rather than 15°37′. That sounds fussy until a planet sits right at the edge of a sign. A Moon at 29.80° Taurus is still a Taurus Moon, and the number shows it.

What people usually ask next

Do I need my birth time for the big three?

For the rising sign, yes, and the place too. For the Sun and the Moon it depends on the day. The Sun changes sign once a month and the Moon every two or three days, so if you were born on a day when one of them moved, the hour decides which sign it was in.

Why do people born on the same day have different rising signs?

Because the Earth turns about 15° an hour, and the sign coming up over the eastern horizon changes on average every two hours. Two people born in the same town on the same day, one at breakfast and one at dinner, will almost always share a Sun sign, probably a Moon sign, and almost certainly not a rising sign.

What do the Sun, Moon and rising stand for?

In Western astrology the Sun is read as your basic temperament, the Moon as your emotional life and instincts, and the rising sign as the first impression you make on people. That is the traditional reading; nobody has measured it. There is more on the rising sign and on the Moon you were born under.

Which time zone does my birth time use?

Once you pick your birthplace from the list, or type its coordinates, OMNIA uses the rules that applied there on the day you were born, from the IANA time zone database, which keeps the history. The United Kingdom, for one, kept its clocks on UTC+1 from February 1968 to October 1971, winters included, so a London birth in January 1970 read as GMT comes out an hour off. With no place set, the time is read in your device's time zone, and the form says which one.

What if I don't know my birth time?

Switch on “Hour Unknown” in the form. You still get the Sun, the Moon, the other planets and the aspects between them. The rising sign and the houses are left out rather than invented. The planets are placed for noon at your birthplace, so pick the place from the list even without the time; with no place set, OMNIA uses noon in your device's time zone, which can be far off. On a day when the Moon changed sign you will need to check it yourself, which takes two extra charts.

Can I see my big six?

Yes. The same planet list carries Mercury, Venus and Mars with sign and degree, and the rest of the way out to Pluto.

Can I keep my big three?

When a reading finishes you can press it into a card showing your wheel, your Sun, Moon and rising, and the balance of elements. There is no birth date, time or place printed on it, and it is drawn in your browser, not uploaded.

What you get

A full natal chart: Sun through Pluto by sign and degree, the Ascendant and Midheaven, Placidus houses and the five major aspects. The positions come from astronomy-engine, an open-source ephemeris good to about one arcminute, and the language model that writes the reading never computes a planetary position.

The chart costs nothing, and neither do Sign, Reading and Whisper, three of the four parts of each reading, up to a daily limit. There is no sign-up and no payment card. The fourth part, Guidance, is for subscribers. Nothing about your birth is stored on our servers.