Work out birth chart positions instantly with clear inputs, formula shown and shareable results.
Solar longitude is estimated from the day of the year, since the sun advances roughly one degree per day, and the zodiac divides that circle into twelve thirty degree signs. For entertainment. The solar longitude arithmetic is real astronomy to within a degree or so, but the rising sign estimate is a rough two-hours-per-sign approximation and ignores latitude entirely.
Solar longitude
longitude = (day of year - 1) / 365.25 x 360 + 280 degrees, wrapped to 0-360
Sign
sign index = floor(longitude / 30)
longitude = (day of year - 1) / 365.25 x 360 + 280 degrees, wrapped to 0-360. Solar longitude is estimated from the day of the year, since the sun advances roughly one degree per day, and the zodiac divides that circle into twelve thirty degree signs.
For entertainment. The solar longitude arithmetic is real astronomy to within a degree or so, but the rising sign estimate is a rough two-hours-per-sign approximation and ignores latitude entirely.
Enter date of birth, hour of birth (24h). The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.