Editing Collimated beam (section)

===Distant sources===
The light from [[star]]s (other than the [[Sun]]) arrives at Earth precisely collimated, because stars are so far away they present no detectable angular size. However, due to refraction and turbulence in the Earth's atmosphere, starlight arrives slightly uncollimated at the ground with an [[astronomical seeing|apparent angular diameter of about 0.4 arcseconds]]. Direct rays of light from the Sun arrive at the Earth uncollimated by one-half degree, this being the [[angular diameter]] of the Sun as seen from Earth.  During a [[solar eclipse]], the Sun's light becomes increasingly collimated as the visible surface shrinks to a thin crescent and ultimately a [[Baily's beads|small point]], producing the phenomena of distinct shadows and [[shadow bands]].