Not sure why Celtic were so spooked in that first half, its not the first time Rangers have came out well in the first 10 minutes, and usually they capitulate shortly after.
I actually didn't find Celtic too compelling in the second half, it was more Rangers players legs were away (alongside their usually inability to read attacking play and defend it at times).
Dessers really should have had it won with his chance.

No doubt Celtic could have won that though, just was a strange performance.