Mount Palomar objects and Geiger-counter reports

Record summary

What happened An observatory astronomer reported 16–18 shiny wingless objects travelling northwest while a Geiger counter in the powerhouse reportedly reached its maximum. Further sightings and counter reactions followed. Tests later found a faulty fuse clip capable of producing false readings, while a Caltech physicist suggested conventional aircraft for the visual objects. Evidence Observatory witness reports, equipment checks and a Project Blue Book file document the episode. Explanations considered Conventional aircraft plus an independent Geiger-counter fault provide a parsimonious two-part explanation. What remains uncertain Timing correlation does not demonstrate that the visual objects caused the instrument response, and no radiation source was measured outside the faulty device. Primary source Mount Palomar objects and Geiger-counter reports — Wikipedia