Fr.: durée de vie de tavelures
The time scale on which a stellar image changes significantly due to → atmospheric turbulence. It is proportional to the ratio r0/Δv, where r0 is the → Fried parameter and Δv the standard deviation of the distribution of wind velocities weighted by the turbulence structure coefficient. Typical lifetimes in the visible range from about 3 to 30 milliseconds.
Omr "life-time;" from Ar. 'umr; pakâl, → speckle.