DOCUMENTARY RESOURCES ON THE HERSCHEL FAMILY
There are several publicly available sources of documents produced by or relating to the Herschel family
The Royal Astronomical Society ( https://ras.ac.uk/ )has a valuable archive of Herschel papers, almost all as a result of donations from the Herschel family, accessible via its website here: https://ras.ac.uk/library/about-the-library%3Fid%3D78
It is divided into four sections: papers of Caroline Herschel (marked HERSCHEL C), of John Herschel (HERSCHEL J), of William Herschel (HERSCHEL W) and books and papers from the Herschel family which do not fall into one of these groups (Herschel Miscellaneous).
The Royal Society ( https://royalsociety.org/ ) also has a substantial collection of papers, particularly relating to John Herschel. The John Herschel collection of the Royal Society comprises 19 volumes of manuscript letters sent to Herschel, with drafts of his replies , as well as additional copy material. A full listing an be found here: https://collections.royalsociety.org/DServe.exe?dsqIni=DServe.ini&dsqApp=Archive&dsqDb=Catalog&dsqCmd=NaviTree.tcl&dsqField=RefNo&dsqItem=HS/3#HERE
More papers related to Caroline and William Herschel can be found by searching for “Herschel” in the Royal Society Archives catalogue: https://royalsociety.org/collections/catalogue-search/
John Herschel papers held by the Royal Society are also included in the Adler Planetarium on line database of his correspondence here: http://historydb.adlerplanetarium.org/herschel/?p=about
The Harry Ransom Center at the University of Texas ( http://www.hrc.utexas.edu/ ) is another major source of papers, particularly relating to John Herschel. They can be accessed using their search engine here : http://norman.hrc.utexas.edu/fasearch/findingAid.cfm?eadid=00568
Other Herschel papers remain with the family, but they can only be accessed by special arrangement.
The Herschel Museum of Astronomy in Bath ( http://www.herschelmuseum.org.uk )has a varying range of exhibits relating to the Herschel family but does not itself maintain a documentary archive on the family.