Constellations are determined by the date of the solar calendar. The solar calendar date of June 16 in the lunar calendar 1968 is July 1 1, and the constellation of that day is Cancer.
Lunar calendar: June 16, Year of the Monkey.
Main branch: Wu Shen didn't leave at noon.
Gregorian calendar: Thursday 1968 July 1 1 Cancer.
Source: Hua Wang.