sextant vs astrolabe

sextant and astrolabe both are nouns.

Word	Noun	Adjective	Verb	Adverb
sextant	Yes	No	No	No
astrolabe	Yes	No	No	No

As nouns, astrolabe is a hyponym of sextant; that is, astrolabe is a word with a more specific, narrower meaning than sextant:

sextant: a measuring instrument for measuring the angular distance between celestial objects; resembles an octant
astrolabe: an early form of sextant

sextant (noun)	astrolabe (noun)
a measuring instrument for measuring the angular distance between celestial objects; resembles an octant	an early form of sextant
a unit of angular distance equal to 60 degrees