Capricorn is the Ascendant when Capricorn was crossing the eastern horizon at birth, which changes about every two hours and therefore depends on birth time. In whole-sign houses, where each sign is one house, Capricorn is the first house. Saturn, the planet that rules it, is lord of the Ascendant. Saturn also rules Aquarius, which falls in the second house, and is exalted in Libra, the tenth. Capricorn is a feminine, cardinal earth sign. It is the Moon's detriment, a concept the tradition names explicitly only late, so the Moon starts from a weaker footing here. Saturn is a malefic, a planet the tradition treats as difficult in nature. It is also a day-team planet under sect, the tradition's sorting of planets into day and night teams. Hellenistic astrologers check its condition, which ranges from supportive to harsh, before drawing conclusions.
A note on “detriment”: the early Hellenistic texts note a planet opposite its own sign without naming it. The term is defined only in late and medieval sources, and scholars disagree on whether the idea was implicit earlier.