Can you put a pop up top on Chevy Astro van?

No, you can't put a standard pop-up camper top on a Chevy Astro van. The Astro's roofline and structure aren't designed to support the weight and forces involved with a pop-up camper's mechanism. The roof is relatively thin and not reinforced in the way a dedicated camper shell is. Attempting to install one would likely cause significant damage to the van's body and roof.