Where? : The active observatory is located on the summit of Mount Hamilton on hwy 130.
What? : You can visit the admission-free Visitor Center (and gift Shop) that are open year-round and take the short informal talks, starting after 12pm (check website).
When? : At winter storms the mountain ridge can get covered by snow. At summer the visibility can be low because of hase.
Due note: The mountain ridge and the surrounding forest were severely damage during summer 2020 fires.
My thoughts: Nice place to visit but not a must.
Additional Nearby parks: