Sentinel moon was located in an unnamed system close to an unidentified gas giant. This meant that the moon was mainly covered in darkness with the closest planets being Geonosis and Tatooine. The atmosphere was toxic to humans. The moon was covered by hills and plagued by violently windy storms that hurled stones and grit. When the moon emerged into the light of the planets yellow sun, the radiance was too intense for human eyes.
In 21 BBY, during the Clone Wars, prefabricated modules were deployed by a Victory-class Star Destroyer to the moon which made up Sentinel Base. Over time, modules were delivered/ assembled on site where by 14 BBY, the base was sprawling in all directions.
In 14 BBY, a group of rebels attacked Rampart Station close by leading to the base being on full alert. After Governor Wilhuff Tarkin analysed what was occurring in Rampart Station, he deduced that a false real time feed of the attack on Rampart Station was placed into the local HoloNet relay. Due to this, he ordered Captain Burque of the Electrum, a Venator-class Star Destroyer, to microjump to the rimward edge of the system where Sentinel Base was. This proved useful with the rebels launching an attack on Sentinel Base. During the battle, the antique Separatist Fighters deployed were no match for the Sentinels Bases turbolasers. By the time the Electum was about to fire a disabling shot on the rebels ship, the rebels left the system.