Palomar divide to observatory?

Just wondering if there was any way to get to the observatory via Palomar divide road. I've only been up there one other time, and I don't remember where but we found a locked gate that says something like "property of cal tech" that I assume goes to it. Any other way? Was thinking that would be a cool day trip as long as the roads are dry. The one wheel wonder doesn't like wet dirt. The last time I went up I was feeling good about my truck...until I saw a little old sentra parked up there