Palomar Observatory between Los Angeles and San Diego) is also open to the public but they don’t have concerts. https://sites.astro.caltech.edu/palomar/visitor/ https://en.m.wikipedia.org/wiki/Palomar_Observatory

Also, if you happen to find yourself around Mauna Kea, HI (watch out for invisible cows!) some friendly telescope employees may be gracious enough to give you a tour. There is also one radio telescope on the mountain that is capable of being arrayed with other radio telescopes (such as the VLA or GBT) for an even longer baseline (and correspondingly higher angular resolution).