The lagna (ascendant, rising sign) is the sign crossing the eastern horizon at the exact minute of your birth, measured in the sidereal zodiac. It is the most birth-time-sensitive point in the chart — it moves about one degree every four minutes — and everything house-based follows from it: which planet rules your chart, where each life-domain lives, which planets act as your allies.
Because Vedic astrology uses the sidereal zodiac (offset from the Western tropical zodiac by roughly 24° today), your Vedic rising sign is often the sign before your Western one. That is not an error — it is a different, astronomically anchored reference frame.
Science of Light computes the ascendant to the arc-minute (Swiss Ephemeris parity, historical time zones handled, Lahiri ayanamsa), names the rising sign and its nakshatra, and reads what it means — free, no account, on-device.
Vedic astrology uses the sidereal zodiac, anchored to the stars; Western astrology uses the tropical zodiac, anchored to the equinox. They currently differ by about 24°, so placements often shift one sign back.
The rising sign changes roughly every two hours, but the degree — which sets the houses — moves every four minutes. A few minutes rarely change the sign; they can change the emphasis. The app flags what is birth-time-sensitive.
Free · no account · computed on your device to ±0.3′ vs the Swiss Ephemeris · methodology