Owned by a private individual in the UK, it has been valued at £108,000.
Auction house Christie’s is negotiating the private sale and the museum has until the end of October to raise the funds.
German-born Herschel (1750-1848) moved to the UK to be with her brother William Herschel (1738-1822) and they began as musicians before later becoming famous astronomers.
They lived at 19 New King Street in Bath, which is now the home of the Herschel Museum of Astronomy dedicated to the many achievements of the siblings. William discovered the planet Uranus in 1781 using a telescope of his own design from the home. Later the pair were joined by William’s son John (1792-1871), who also became an astronomer.
Among Caroline’s achievements was the discovery of several comets including the periodic comet 35P/Herschel–Rigollet.
The museum said that much of its collection is on loan and of the items that are owned, just one was made by the Herschels, which makes acquiring this memoir for the permanent collection a very high priority.
Christie’s describes the manuscript as of “extreme rarity and with a direct family provenance: the present manuscript has never previously been offered for sale”.
Izzy Wall, assistant curator, has researched the manuscript. She said: “It was written around 1836 when she was 86, in English, with occasional passages or words in German. The chapters contained in this draft cover the years 1755-75, a crucial period of Caroline’s life, from her childhood in Hanover to early years in Bath.
“It provides a valuable insight into the Herschels’ life in Bath, Caroline’s education and her struggles when she arrived in England. It also contains important insights into the Herschels’ professional lives as musicians in Bath, William’s increasing interest in astronomy and his telescope-building endeavours.”
Claire Dixon, director of Museums for Bath Preservation Trust, added: “There is a significant risk that if the museum is unable to purchase the manuscript, it will be bought by one of the American institutions that collect Herschel material. Should this happen, public access to the manuscript here in the UK will be lost. By securing this object and putting it on display at the museum, here in Caroline and William’s former home, visitors will be able to directly engage with Caroline’s story, literally through her own words.”
In March the museum bought a visitor book that had been owned by collectors Dr and Mrs A Koester.
To read more about the fundraising visit The Herschel Museum of Astronomy.