I have been reading the Pact Worlds book and it came to attention that the Free Captains have their headquarters based in the Pact Worlds system which is home to various factions that would like to see them dead. Their headquarters know as the Broken Rock is a 450-mile-wide asteroid (similar to Ceres) so it's not exactly hard to notice. The only explanation as to why this asteroid has not been atomized is:
To keep law-enforcement organizations such
as the Hellknights and the Stewards off these ne’er-do-wells’
backs, only Free Captains and those they vouch for know the
exact location of Broken Rock. In the event of an attack, an
array of automated capital laser weapons known collectively
as the Broadsides defends the asteroid.
Pact Worlds pg 82
You would think factions like AbadarCorp, Stewards, Hellknights, Knights of Golorion, and the various militaries of the Pact Worlds would have the resources to track down this one base that has been used for centuries.