Hope the article gave some idea of the Navigators job on Bostons, there is also a posting on the internet by family of a Boston navigator of 88sqn on D-day.
BBC - WW2 People's War - My D-Day Experience 6th June 1944: 88 Squadron RAF
My father was also on the D-Day raid laying smoke from G-Glenda and flew a second sortie that day to support the Invasion troops near Caen.