is it possible to knock out someone in sleep without being seen?

[Cemlat]

as title, I tried save and reload few times, even if hit the button at right time, they know its me in the morning. So whats the catch? I don't want to kill them just to steal things. My visibility is low but I wonder if I have to cover my head somehow if thats even possible.

[Arden]

I was able to do it without consequences with all stealth stats under 20. But the person must not be close to another. It's best if it's a single person in a bedroom or something. Also they don't stay out all night. So you better do the takedowns last and get out of there asap.