The next time you're having one of those observing sessions where nothing seems to go right, or the light pollution is being a bit of a problem, consider this observing log entry:
...started exposure at 21h 44m GMT. Flying bomb exploded very close and shifted star in declination out of the field. Star recovered and exposure restarted at 21h 47m GMT. Just after starting the second time, a second flying bomb exploded. This was more distant and though it shifted image from the slit, star did not go out of field and was quickly recovered. Exposure ended 22h 07m GMT.From here, via this posting on the SPA BB.
File Under: World War II, Observing Problems.