Etymology
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astronomical (adj.)
1550s, "pertaining to astronomy," from astronomy + -ical. Popular meaning "immense, concerning very large figures" (as sizes and distances in astronomy) is attested from 1899. Astronomical unit (abbreviation A.U.) "mean distance from the Earth to the Sun," used as a unit of measure of distance in space, is from 1909. Related: Astronomically.
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nebular (adj.)
1821, "pertaining to an (astronomical) nebula or nebulae," from nebula + -ar.
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oppositional (adj.)

"of or pertaining to opposition," 1680s, from opposition + -al (1). Originally in the astronomical sense of opposition; the general sense of "having the character of hostile action" is from 1829.

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Schmidt (n.)

type of astronomical telescope lens used for photography, 1939, named for Estonian-born German optician Bernhard Voldemar Schmidt (1879-1935), who is said to have invented it.

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photosphere (n.)

1660s, "orb of light, envelop of light," from photo- "light" + sphere. Astronomical sense "luminous envelop around the sun (or another star)" is from 1848. Related: Photospheric.

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longitude (n.)
late 14c., "length; height," also "astronomical or geographic longitude," a measure of the east-west distance of the dome of the sky or the surface of the earth, from Latin longitudo "length, long duration," from longus "long" (see long (adj.)). For explanation of the geographical sense, see latitude.
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globular (adj.)
"globe-shaped, round, spherical and compact," 1650s, from French globulaire or Medieval Latin globularis, or directly from Latin globus "round mass, sphere, ball" (see globe (n.)). Earlier in same sense was globical (1610s). Astronomical globular cluster attested from 1806.
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nutation (n.)

1610s, "action of nodding," from Latin nutationem (nominative nutatio), noun of action from past participle stem of nutare "to nod," from PIE *neu- (2) "to nod" (see numinous). Astronomical use in reference to slight periodical oscillation of the earth's axis is from 1715. Related: Nutational.

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quartile (adj.)

mid-15c., "90 degrees apart" (of the relative position of two heavenly bodies in astronomical measurements), from Old French quartil, from Medieval Latin quartilus "of a quartile," from Latin quartus "the fourth, fourth part" (related to quattuor "four," from PIE root *kwetwer- "four").

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interstellar (adj.)
1620s, "situated between or among the stars," in reference to the night sky (modern astronomical sense is from 1670s), from inter- "between" + Latin stella "star" (from PIE root *ster- (2) "star"). Intersiderial in the same sense is from 1650s.
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