Apollo 12 entered lunar orbit on November 18, 1969 by firing the Service Module engine for just under 6 minutes.

The next day, Conrad and Bean entered the Lunar Module and undocked from the Command Service Module. They performed a short 30-second burn of their Lunar Module descent engine to lower their orbit to a point where they could refire their engine and attempt a landing.

Apollo 12 Lunar Module Intrepid shortly before it descended to a lunar landing.