Avatarika
अस्तमित आदित्ये, चन्द्रमस्यस्तमिते अग्निर्ज्योतिः ॥
In plain words
Once the sun goes down, and the moon goes down after it -- fire is what is left to light the way.
Close to the Sanskrit
When the sun has set, [and] when the moon has set, fire is the light.