The Blue Moon Fund (also known as Cassiopeia Foundation) is a left-of-center grantmaking institution based in Charlottesville, Virginia. According to the organization’s website, it has completed a sunset strategy and ceased grantmaking. 
The Blue Moon Fund, known since 2016 as the Cassiopeia Foundation, is a defunct private foundation that was based in Charlottesville, Virginia. Diane Miller and Patricia Edgerton organized the Fund.
The Blue Moon Fund was born out of a breakup of the W. Alton Jones Foundation. The W. Alton Jones Foundation was created by former oil executive Alton Jones in 1944 from oil revenues of the Cities Service Company. By the end of the 20th century, the Jones Foundation was dissolved by Jones’s family after his death amid a dispute on the future of the non-profit. 
In 2001, after a family disagreement about the direction of the W. Alton Jones Foundation, the children and grandchildren of Alton Jones decided to split the W. Alton Jones Foundation into three distinct entities: The Blue Moon Fund, the Oak Hill Fund, and the Edgerton Fund. 
After the dissolution of the W. Alton Jones Foundation, the almost $400 million endowment of the foundation was split between the Oak Hill Fund, the Blue Moon Fund, and the Edgerton Fund.  Prior to the Blue Moon Fund’s dissolution in 2016, the fund had over $113 million in assets.  The Cassiopeia Foundation, in its latest 2016 tax return, shows $99 million in assets for distribution. 
The Blue Moon Fund provided grants to environmental groups in three areas of the world: Asia, North America, and South America. The grants were targeted towards resource implementation, energy use, and environmental conservation.  Between 2001 and 2014 the Blue Moon Fund had provided $130 million in grants in 650 instances.  Annually, the Blue Moon Fund had provided, on average, $12 million a year in grant making to organizations across the world. 
Organizations Blue Moon funded included the World Wide Fund for Nature (formerly World Wildlife Fund), Sierra Club, Natural Resources Defense Council, Environmental Working Group, Greenpeace, the Nature Conservancy, Friends of the Earth, Worldwatch Institute, Environmental Defense Fund, and affiliates of the League of Conservation Voters. 
In 2005, Diane Edgerton Miller, the then CEO and President of the Blue Moon Fund, was on the International Board of Directors for the Global Environmental Institute based out Beijing, China. Partners of GEI included the People’s Republic of China National People’s Congress Environment and Resources Committee and the Central School of Communist Party, among other Chinese government entities.