The man made the call, not thought to be a prank, in a state of panic saying the object's 'lights were blazing'.
However, just moments later the caller phoned back the operator to say he had mistaken the UFO for the moon.
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Whoops! An emergency 999 caller summoned police after spotting a mysterious object hovering above his house only to find out it was the moon
The call was made earlier this month and was initially treated seriously by the force.
The caller, who rang police just after 8pm, is heard telling police he can see a mysterious flying object coming towards his house with lights blazing.
He said he was in the Canterbury and Stevenage area of Hertfordshire.
The call handler asked him if he could hear engine noises but he said he couldn't.
The call handler spends several minutes writing up his description of the sighting and then says she will contact the local police team to see if they know anything about it.
Jason Baxter, assistant manager at the force communications room, said: 'While the caller here may not have been phoning out of malice, his call still tied up valuable police resources and time for something which was not an emergency.
'It also illustrates the kind of bogus call we might receive to 999, whether as a hoax or an inappropriate call.
Police 999 call handlers, like these pictured, say this call about the moon tied up valuable police resources which could have been used elsewhere
'And is this really an emergency call - an immediate threat to life or property?
'If this is not a police matter, please do not call us. Otherwise you could potentially put others with genuine police or emergency calls at risk or prevent them from getting through.
'Also, if you are thinking it would be funny to play a 'trick' this Halloween and make a hoax call, be very careful.
'You could find the 'trick' is on you when we prosecute you for making a hoax call.'