Uranus' rotational period

A modified spectroscopic technique yields a value for Uranus' period of 23_?2⁺⁵ hr, which disagrees with the accepted value of 10.8 hr determined spectroscopically in the 1930s. Uranus' rotational axis is probably close to the perpendicular to the orbital plane of the satellites, as often assumed. Its projection on the plane of the sky is within 5° of the projection of the normal to the orbital plane of the satellites.