murse gismu

x1 is the [astronomical] twilight/dawn/dusk/half-light/glimmering of day x2 at location x3.

Morning twilight, dawn (= cermurse); evening twilight, dusk (= vacmurse). See also cerni, kandi, vanci.

In notes:

cerni
x1 is a morning [dawn until after typical start-of-work for locale] of day x2 at location x3.
kandi
x1 is dim/dull/pale/non-intense in property x2 (ka) as received/measured by observer x3.
vanci
x1 is an evening [from end-of-work until sleep typical for locale] of day x2 at location x3.