Starship Asterisk*

Mysterious Green Patches on the Sky

Kevin Snair wrote:Good evening,
I am the photographer who created this video. I'd like to thank everyone for actively helping solve this curiosity. Many questions have been asked so I will try to fill in some of the gaps.
I am a professional photographer who lives and works near The Hopewell Rocks in New Brunswick, Canada. A gentleman was in the park early this season and introduced me to the fun of night photography. I played around with the technique with pleasing results so I decided to try a time lapse video. My first attempt was done during a new moon in early July. I started rather late in the night and went through till dawn. It can be viewed here: https://www.youtube.com/watch?v=_4N5rCm5b7g
I had a small glitch in the evening resulting in me losing 7 minutes of photography. This shows in the video as a jump in the stars just as the milky way passes over Lover's Arch. Being a little on the anal side, this bothered me enough that I felt I wanted to re-do it.
On the evening of August 11th (and into the morning of the 12th) I set up my equipment again. The Hopewell Rocks is situated on the Bay of Fundy which is known for the highest tides on the planet. I set up my camera (Canon 5D mkII) on a tripod down on the shore facing approximately South East. I had the tripod at a height where the tide would rise around it but the camera would be above the high tide mark. I could have set up the tripod above the high tide mark but then I would not be pointing into the sky and still having the Rocks in the foreground. Please keep in mind I was creating this for aesthetics, not a scientific experiment. I set my ISO to 5000, the shutter speed to 30 seconds and the fstop to 4.0 (canon 17-40 mm lens at 17mm focused at infinity). I knew my first hour would be severely overexposed but as the sunset disappeared, the exposure would eventually be right for the remainder of the evening. The results were a gradual fade from white to night sky. I took my first shot at 9:19 pm and continued to take one shot every 40 seconds until 3:08 am. I had set up two small Colman battery powered LED lanterns to illuminate the rocks. They are the source of exposure on the rocks and beach.
It was a beautiful evening, quite warm and no moisture built up on the lens. I was awake and present for the entire event. The camera was being controlled by a laptop and I checked it on occasion to see that everything was working. When opening the laptop, occasionally the screen would add a bit of light to the closest rocks (explaining small fluctuations in foreground exposure). As the tide rose, I did not see the green "clouds" with the naked eye but it was extremely dark and the camera's sensitivity was allowing it to capture more than I was seeing. The tide was coming in with one to two foot waves and I realized that my camera would not survive the entire evening. I stood in water up to my waist, supporting the tripod but eventually the waves forcibly moved the camera and my shoot was over. It is worth noting that as the tide rose, it physically moved my foreground light (changing my foreground exposure as noticeable on the right hand rock surface).

When I got home and processed the photos, I did the following to all 508: Set white balance to 4350, increased the exposure by 15%, added a bit of fill light (midtones +45), and increased the saturation by 10%. When I turned them into the video, I faded to black at the very end to make it more pleasing to the viewer.

Kevin Snair wrote:Here are links to two stills. One is prior to the arrival of the green. The other during.

Http://www.creativeimagery.ca/Persieds_367.jpg
Http://www.creativeimagery.ca/Persieds_424.jpg

LedZeplin wrote:My guess before I read the other replies was clouds or haze with the white balance on the camera causing the green tint. Some of the other ideas are fun, but I'd ask what rules out a simple camera error. Is there an eyewitness who corroborates that the camera captured accurately what was observed with a human eye?

Curt wrote:My guess is the light source that is hidden behind the foreground rock, illuminating the other rocks with a greenish hue, is then reflecting off the incoming tide water, and illuminating the bottoms of the low clouds (fog) hovering just above the waters.

Curly G wrote:I agree that there is a strong correlation with the tide, but there are also some good arguments for an artifact of the digital camera. I would think that this could be resolved with experimentation - go to the same location, with similar tidal and weather patterns, and attempt to reproduce the effects, while also diligently recording all atmospheric phenomenon (temperature, winds, humidity). Then try the experiment again at different locations.

Surely all that government funding could be put to good use!