This answer to Any record of the Earth passing through the tail (not trail) of a comet? mentions
Earth passed through the tail of Halley's Comet in 1910. It caused a bit of a panic due to claims that cyanogen detected in the tail would cause harm: https://en.wikipedia.org/wiki/Halley%27s_Comet#1910
and links to the February 8, 1910 New York Times item Comet's poisonous tail; Yerkes Observatory Finds Cyanogen in Spectrum of Halley's Comet
This comment reminds us that its appearance was not unanticipated:
Astronomers of that time certainly knew when to expect Halley's Comet. After all, this was its third appearance after Edmond Halley's famous prediction. It seems reasonable to think that Wells & much of the general public would have also known it was coming.
And this comment reminds us:
H G Wells wrote "In the Days of the Comet" in 1906, in which the earth passes through the tail of a comet. I don't know if astronomers of the time had predicted the Halley event 4 years early: In the Days of the Comet
Question: What exactly were astronomers expecting prior to the comet's arrival? Did they have a predicted orbit, time of appearance and closest distance to Earth and estimated brightness prepared? If so, how close did the predicted behavior match the actual?
Was there any prediction or concern about the Earth passing through the comet's tail?