Hadith.678 - Umar ibn Hanthala asked Imam Jafar ibn Muhammad Al-Sadiq (as) saying:
"We recognize the zenith (midday) of the sun during the day; how can we recognize the zenith during the night?"
Imam (as) said: "The night has a zenith just like the zenith of the sun."
Umar then asked: "And by what means do we recognize it?"
Imam (as) said: "By the stars when they descend”.