An old book
The Herschels and Modern Astronomy by Agnes Clarke, 1895
https://ia800208.us.archive.org/17/i...4012300681.pdf
Attached is John Herschel's description of the 1837 outburst of Eta Carinae on page 168.
It was as bright as alpha Centauri then and later as bright as Canopus for 7 years!