 Turner envisioned this as a black man's hand reaching over the sun.Turner originally planned to begin the rebellion on July 4, Independence Day, 1831, but he had fallen ill and used the delay for additional planning with his co-conspirators.An atmospheric disturbance on August 13 made the sun appear bluish-green, possibly the result of lingering atmospheric debris from an eruption of Mount St. Helens in present-day Washington state; he took it as the final signal and began the rebellion a week later, on August 21.