Strange light beamed straight down over our campfire. There was no sound.

My family's old cabin is located at the 5000 ft elevation level in the Sierra Nevada Mountains.  It rests in a small valley surrounded by hills on both sides and a small creek runs about 30 feet to the east.  
Late in the evening, what looked like a helicopter search light suddenly beamed straight down over our campfire.  My husband noticed it first.  He said, "((name deleted)), it's a UFO! There's no sound!"  The margins of the light were well defined and shined from about 80 feet up at tree top level.  After about 10 seconds it began "searching" the area in a mechanical sort of way.  It shined on us for about 10 seconds and disappeared. I could not see the shape of the craft due to the brightness of the light.  There was never any sound.  My husband was terrified but calmed down quickly.  I remained calm the entire time and told him that there must be a logical explanation for this.  There was an eerie quietness in the air afterwards I felt slightly whoozy.  Soon after the incident we went to bed.  My husband made mention that it was very weird.  Oddly, we never spoke of it to each other again. That was about thirty years ago.  It wasn't until recently that I came to realized just how strange that whole event was including our odd behavior afterwards.  It is especially strange in view of the fact that I find the subject of UFOs facinating and always have.  I don't know what to make of it.
Witness indicates that the date of the sighting is approximate.  PD