Learn French: Vous voyez les étoiles quand ?

Voyez is the vous form of the irregular verb voir (to see). For the nous and vous forms, the 'i' changes to a 'y', giving us nous voyons and vous voyez. The other forms keep the 'i', like in je vois or ils voient.

Why is the word quand at the end of the sentence?

In everyday spoken French, it is very common to keep the standard subject-verb word order and just put the question word at the very end. You could also ask Quand est-ce que vous voyez les étoiles ?, but this shorter version is very natural in casual conversation.

Do I pronounce the 's' in les?

Yes, you do! Because étoiles starts with a vowel, you must make a sound connection called a liaison. The 's' in les connects to the beginning of étoiles and is pronounced like a 'z'.