This page relates to the Astronomy Picture of the Day for 7th December 2004, which shows an unusual streak and flash on a daylight photograph. Many varied suggestions have been made as to the cause, ranging from meteors and exploding lamps through to shadows and insects flying in front of the lens. Viewers were challenged to find an explanation for the image; in order to help determine the most likely explanation, this page presents a collection of results obtained both by applying various signal processing techniques to the image in question and by physical experimentation.

Click images for larger versions

The image on the left shows just part of the original, and the trail can just be seen travelling from the upper left corner to the lower right. By comparison the image on the right is a processed version of the full picture which reveals the trail (and the object at the end of it) in more detail. It's evident from the procesed version that the trail both starts and ends within the image, which tends to exclude a lot of explanations (in particular, it excludes the meteor theory since the speed of a meteor is such that it would have crossed the whole frame during the exposure).

One of the explanations was that an insect, possibly a bee, either flew or was blown past close to the camera during the exposure. Because it was close to the lens, it left a long trail behind it as a result of motion blur. This seemed a reasonable explanation, and this theory was used as a guide in deciding what experiments and tests to make.

Results and Explanations

• An explanation of the Insect Theory
  
• Experimental reproduction of the trail and object
  
• Enhanced and processed images of the trail and object
  
• Initial and final determination of the trail shape
  
• FFT analysis of the trail
  
• Methods and materials
  

Links:

• The Astronomy Picture of the Day that started it
  
• Before Image, Event Image, and After Image
  
• A difference image
  
• Discussion forum