Sectar is a planet in the Zeta Quadrant of Cyrannus. It is home to the native Borays, as well as a small agro colony of humans, settling in the town of Serenity. As with other far-flung settlements, it was cut off from the Colonies sometime during the Thousand-Yahren War.
In more recent history, the Borays began raiding Serenity for food, supplies, and women when Sectar's orbiting satellite became fully visible in the night sky.
Adama leads a mission to this planet hoping to trade an unmarked energizer in exchange for some agron seed, after two of the three agro ships in the Fleet are destroyed during a Cylon attack (TOS: "The Magnificent Warriors").