Amateur
- 503
- Mount Diablo Astronomical Society
- Public program, newsletter, meetings, outreach program, gallery, and satellites based in Walnut Creek.
- 504
- Mountain Skies Astronomical Society
- Gift shop, astronomy village, star atlas, calendar of events, news, and basic information located at Lake Arrowhead.
- 505
- Orange County Astronomers
- Located in Costa Mesa and provides calendar, e-zine, resources, and gallery.
- 506
- Peninsula Astronomical Society
- Provides courses, news, evening and solar viewing information, and special viewings located in Los Altos.
- 507
- Polaris Observatory Association
- Provides telescope and camera information, gallery, and astrophotography information.
- 508
- San Diego Astronomy Association
- Outreach, events, resources, merchandise, utilities, and telescope loaner utility page.
- 509
- San Francisco Amateur Astronomers
- Bulletin board, meetings, lectures, star parties, calendar, newsletter, and photography.
- 511
- San Jose Astronomical Association
- Star parties, lunar eclipse information, hints for beginners, star party etiquette, and activities.
- 512
- Santa Barbara Astronomical Unit
- Monthly events calendar, night sky, events, newsletter, archive, photo album, classifieds, and dark sky sites.
- 515
- Sonoma County Astronomical Society
- Calendar, events, activities, beginners information, and gallery located at Santa Rosa.
- 516
- Stockton Astronomical Society
- Activities, services, newsletter, astro-kid section, gallery, and links.
- 517
- The Antelope Valley Astronomy Club
- Calendar, observing and planetarium information, essay contest winners, and photos located at Lancaster.
- 518
- The Eastbay Astronomical Society
- Astro advice, constellation chronicles, newsletter, workshop, schedule, and gallery located in Oakland.