Arcsecond
One milliarcsecond (mas) is a thousandth (1/1000th) of an arcsecond. So there are 1,296,000,000 milliarcseconds in a full circle. The red supergiant stars Antares, Betelgeuse, Mu Cephei, VV Cephei A, and VY Canis Majoris all have angular diameters (apparent sizes in the sky) of more than 10 milliarcseconds, when seen from Earth.