VENUS

The proper rotation of this planet has long been remained unknown. 
In 1957, Charles Boyer measuredit by observing in the ultraviolet wavelength, and finds a period of 4 days. But in 1962, through radioastronomy, a rotation period of 243 days was found. 

In fact, Boyer measured the period of rotation of the clouds, while on the ground, the period is actually 243 days. The image at left, made by Mariner 10 in the ultraviolet in 1974, shows the dynamics of the atmosphere of Venus.