Umbra.

x

—

y

—

d

—

l1

—

l2

—

μ

—

tan f1

—

tan f2

—

γ

—

x and y place the Moon on the fundamental plane, in Earth radii. l1 and l2 are the penumbral and umbral shadow radii there. l2 < 0 means total, l2 > 0 annular.