When Halley's Comet is visible in the sky, how long does that last? Is it only visible for a week or is it up there for a month, or several months? What I'm actually wondering is, though it arrived in 1910, could it still have been visible in the sky into 1911?
Typically it was visible a few weeks only, about 3...6 months at most. There is an excellent summary in Broughton (1979). In 1910 the peak visibility was in April, the last recorded sighting of Halley without instrumentation on 13th June. Yeonan (1986) gives an overview including instrumentation; while it has positional and brightness data for dates in 1911, they are for a magnitude > 10, thus far beyond being visible with the naked eye.
So no, in 1911 Halley was not visible anymore without then bleeding-edge astronomical telescopes.