First Light 

When a telescope or astronomical instrument is first used to take an image after construction.

I just started to build a 100 meter optical telescope in my backyard: first light will be in 2038.

First Light by LegitSciNtech August 22, 2011

First Light 

The first lighting of the sky after night and before dawn when the stars begin to dim. Surfers first check the waves at this time.

Hey dude, I'll meet you at Cardiff at first light to shred the gnar-gnar.

First Light by NatureGirlENC May 26, 2018

love at first light 

Waking up in bed with someone, not remembering the night before, but instantly falling in love with them as soon as you open your eyes.

Johnny didn't remember how he got there, but when he woke up in the morning next to Mary he knew that was where he wanted to wake up the rest of his life - it was love at first light.

love at first light by Pseudojohnny April 13, 2016