It's just been closed for tours and public events. It's not the same, but you can take a virtual tour here: https://sites.astro.caltech.edu/palomar/visitor/virtualtour....
It’s truly time to let covid fears subside and fade away.
I’m much more concerned with irrational people who get angry with someone not wearing a mask than I am that the person not wearing a mask would be a risk to me.
Of course, and thankfully unhinged zealots are a small percentage of potential visitors. Still, my point is that it's hard to blame institutions that aren't mandated to have public access for avoiding the entire issue.