What Is An 'Ascendant' In Astrology?
If someone says, "I'm a Pisces" and asks your sign, you probably understand what they're talking about: astrology, your monthly horoscope, the twelve houses of the zodiac, that sort of thing. Each sign of the zodiac is a constellation seen from Earth — Sagittarius is an archer, Leo is a lion, Capricorn is a ram, and so on. As Earth rotates, revolves around the sun, and wobbles on its axis, various constellations show up in the night sky at different times, and voila: they purportedly exert influence on human activity. Such beliefs form the bedrock of numerous ancient cultures, most notably in India.
Regardless of whether or not you "believe in" this kind of thing, it's accurate to say that much of astrology goes unknown. For example, the whole "what's your sign" thing refers only to one's "sun sign," which is one small aspect of a mammoth astrological birth portrait that includes all the planets, various celestial bodies, the moon, and more. This makes sense because there are about 8 billion people alive with way more than twelve personalities (per The World Counts).
A sun sign shows which constellation was behind the sun in the sky when someone was born and represents a summary of their personality. By contrast, a "rising sign" — also called an "ascendant" — depicts how you come off in public. It's the "you" that others see.
Social 'vibe' and expression of ego
If you've ever felt one way and acted another, then it's easy to understand what an "ascendant" represents. For instance, maybe someone who appears totally outgoing at a party actually feels intense social anxiety. In this case, the "vibe" they put off around others is actually a counterbalance to a deep and opposing inner world.
As Well and Good very excellently puts it, you can imagine a sun sign being a lens through which inner needs are expressed. An expressed image gets projected through this lens (sun sign) into a movie you see on a screen. The "movie" is one's ascendant. It's the self others see when deep, unconscious drives become attenuated by individual personality or ego. And so, astrologers often refer to one's ascendant as the "divine path" along which someone moves. It's the guide projected in front of you that lights the way forward, so to speak, and indicates the way to resolve inner needs and grow as an individual. And for the record, those deep, unconscious drives are articulated by one's "moon sign" — the constellation behind the moon when you were born.
As Allure explains — and in keeping with the symbolism of "the you that others see first" — astrologers calculate someone's ascendant by looking to what constellation was in the furthest point along the horizon at birth. This is why comprehensive astrological charts ask for an exact birth time, as it has such a huge impact.