The Celestial Sphere │ Sphera cælestis
[i] caelestis, -e: heavenly < caelum, -ī [2/n]: sky; heaven
alternative spellings: coelestis, -e; coelum, -ī [2/n]
caelestia, -ium [3/n/pl]: heavenly bodies
[ii] Note the spelling shift of CL sphaera > post-Classical / Mediaeval: sphera > Engl. deriv. sphere; this is a regular shift
[1] Astronomy considereth the motion of the stars, astrology the effects of them. │ Astronomia cōnsīderat mōtūs astrōrum, astrologia eōrum effectūs.
[i]
astrum, -ī [2/n]: star
astronomia, -ae [1/f]: astronomy
astrologia, -ae [1/f]: astrology
“These terms were at first synonymous expressions among the ancients, both signifying ‘the science of the stars.’ But afterwards astrology came to mean that part of the science which deals with the supposed influence of the stars on the destinies of men.”
https://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0062:entry=astronomia-harpers
[ii] mōtus, -ūs [4/m]: motion
effectus, -ūs [4/m]: effect
Many 4th declension nouns are formed from perfect passive participles:
moveō, -ēre, mōvī, mōtus [2]: move > mōtus, -ūs [4/m]: movement; motion
efficiō, -ere, effēcī, effectus [3-iō]: accomplish > effectus, -ūs [4/m]: accomplishment; effect
Similarly:
audiō, -īre, audīvī, audītus [3]: hear > audītus, -ūs [4/m]: (the sense of) hearing
olfaciō, -ere, olfēcī, olfactus [3-iō]: smell > olfactus, -ūs [4/m]: (the sense of) smell
tangō, -ere, tetigī, tāctus [3]: touch > tāctus, -ūs [4/m]: (the sense of) touch
videō, -ēre, vīdī, vīsus [2]: see > vīsus, -ūs [4/m]: (the sense of) sight
