Sunday, June 19, 2005

A good night time view of Mount St Helens, and a further mystery

The sky was clear last night and there was a stunning view of the lavadome glowing in the night and also illuminating the rising steam plume in the early part of the evening. See the animation and images here.

The mystery glow on the western flank was visible, as was another glow in front of the crater! e.g. see this stacked image from last night (the second glow is the small dot below the crater and to the left of the centre of the image):




I have been going back over the last several months of images and it is obvious that this second glow has been visible intermittently for many months. So it looks like these anomalous glows are probably hot pixels in the Volcanocam - although I am still a little perplexed as to how a "hot pixel" can vary in intensity (and number of pixels) so much from day-to-day and throughout a single night. After all, if a defective pixel is hot, it would be expected to stay hot all the time and if it was affecting nearby pixels, why would it vary in its effect by so much? I will post examples of the images and some animations later this week on my Mount St Helens page so you can make up your own minds about what is going on.

3 Comments:

Anonymous Anonymous said...

It could, of course, be a hot pixel but in last night's sequence it almost appears as if there is a plume or "puff" along with the second glow that appears to be going toward the left in the picture from the point of glow.

Does the "hot pixel" appear on cloudy nights? Could there be a small hot spring or fumarole there? Can a time exposure with conventional IR sensative film be made and compare with the camera image? Maybe another low light CCD camera and a comparison? What about a IR imager like that which is used to take the thermo images of the dome? If one were used at night when the temperatures are lower, it might spot a thermal anomaly that might not be visible when it's warmer.

I just have a hard time believing that it is just a hot pixel since it appears to fuzz out and I would expect it to be a nice, sharp, hot pixel and fairly binary ... on or off.

2005-06-20, 12:40 AM  
Anonymous Anonymous said...

As I mentioned in a private email, if the USFS would only re-aim the camera toward the right, we might be able to see more. If they do that, then the dome will be on the left and the glow will be more toward the center of the image if the problem is on the mountain. If the glow remains in the same spot on the image, then the problem is in the camera. This seems to me to be a very easy way to check the origination of the glow.

2005-06-20, 8:08 AM  
Blogger Daz said...

The hot pixel(s) do appear on some cloudy nights, but not all. That's why I originally thought that this must be due to a real source originating on the mountain.

I have just posted a couple of close up images of the area, which do not seem to indicate any possibility of hot springs/fumarole activity.

I suspect that this is caused by some sort of defective pixel(s) and the cause of the variation in intensity over time is due to the processing of the images after they are captured by the Volcanocam camera, but before they are transmitted to the USFS server and posted on the web.

I hope to post some more detailed info on this soon.

2005-06-20, 10:01 PM  

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