Little Basin is the former HP Employee campground, off highway 236 on the southern reaches of Big Basin State Park. Normally, this site is available to registered campers only.
note this site is 1.7 miles up a narrow very bumpy barely paved road from highway 236, so its a fairly serious drive. From just north of central Santa Cruz, it takes me about 30-35 minutes when I drive briskly.
I, in the guise of the Santa Cruz Astronomy Club, have made arrangements to setup there on selected Saturday evenings and offer star gazing to the campers. As SCAC has a fairly small set of dedicated star party goers, and we've already got a number of other dates on our calendar, these aren't as frequent as the camp Interpreters would like, so if a group of responsible TACo's wants to add some dates, contact me, and I'll put you in touch with the ranger to schedule. The site could handle a dozens of astronomers + telescopes, however they likely want to minimize traffic in/out due to the narrow gnarly road.
The observing site is a large 'terraced' meadow that serves as the campgrounds overflow parking lot. overflow parking rarely uses more than the east third of the lower two terraces, so we've been setting up in the middle of the 3rd terrace. There's tall trees around this meadow, so horizons aren't great, but its quite dark, seeing has been variable this winter, as has tranparency, with a couple really good nights. Some nights, there's been heavy dew. this spring, there have been quite a few mosquitoes at twilight but they seem to go away later.
the setup spot is around 37°09'25.6"N 122°12'11.2"W
or 37.157126,-122.203120 if you prefer.https://www.google.com/maps/d/embed?mid=1X3GUPyNiXkF63MnI98VwkSi4Bn8
from the south bay, you'd take highway 9 to Boulder Creek however you like, then 237 towards Big Basin State Park, turning left on Little Basin Road at the top of the hill.