How Does The Descendant Sign Calculator Work?
The Descendant is calculated by adding 180 degrees to the Ascendant's ecliptic longitude and reducing the result modulo 360 degrees. The zodiac is divided into twelve equal 30-degree signs, so this operation always places the result in the sign directly opposite the Ascendant.
Formula: Descendant Longitude = (Ascendant Longitude + 180°) mod 360°. For an Ascendant at 45°, the Descendant is 225°, corresponding to 15° Scorpio. This arithmetic is exact for a known Ascendant longitude, regardless of the symbolic interpretation attached to the result.
If you already have a natal chart, look for ASC and DSC markings on its horizon axis. The Descendant is the western endpoint. To obtain your Ascendant from birth information, use a chart calculation that accounts for the correct historical time zone and geographic coordinates.