It’s a century since Hubble announced his discovery of the variability of the nebula NGC 2261 in Monoceros. His brief paper on “CHANGES IN THE FORM OF THE NEBULA N.G.C. 2261”, was received by the journal, the Proceedings of the National Academy of Sciences, on March 9th 1916. A more detailed analysis was published a few months later in the Astrophysical Journal.
A recent BAA news article on the nebula and how to observe it was posted by Stewart Moore, “Hubble’s Variable Nebula: A deep sky object that does something”, at https://www.britastro.org/node/7090