tsani -tan- gismu

x1 is an expanse of sky/the heavens at place x2; [celestial].

See also gapru, kensa, tarci, terdi.

In notes:

gapru
x1 is directly/vertically above/upwards-from x2 in gravity/frame of reference x3.
kensa
x1 is outer space near/associated with celestial body/region x2.
tarci
x1 is a star/sun with stellar properties x2.
terdi
x1 is the Earth/the home planet of race x2; (adjective:) x1 is terrestrial/earthbound.
tanblo
x1 is an airship for carrying x2, propelled by x3
tanminli
x1 is x2 (default 1) parsec(s) by standard x3.
tanta'o
t1=t1 is a skysurfingboard of material/property t2.
zei'e (exp!)
marks a construct as used for its form only, not its meaning.
aksarni
x1 is aurora borealis