Star Captain is a mid-level officer rank within the Clan military structure. A Star Captain commands either a Binary, Trinary, or Supernova unit. A larger commission would typically include 10 MechWarriors, 50 Elementals, 35+ serviceman for the related equipment, plus additional functionaries (or the equivalent numbers for Aerospace fighters, Protomechs, etc).
Star Commanders usually require years of exceptional service before being promoted to Star Captain. Alternatively, a sibko cadet can test into the position by defeating three opponents during his/her Trial of Position, an exceptional and extremely rare event. Star Captain is the highest rank a Clan warrior can achieve without having a Bloodname.
Clan Blood Spirit
Clan Cloud Cobra
Clan Fire Mandrill
Clan Hell's Horses
Unlike most other Clans, there is an official Nova Captain rank available to warriors in the Hell's Horses touman. These officers command a Binary or Trinary of Novas. With the increased number of troops under their command (double that of the typical Star Captain) a Nova Captain could be considered equivalent to an Inner Sphere Major.
Clan Wolf/Clan Wolf-in-Exile
References