Wednesday, June 22, 2005

A cloudy night on Mount St Helens

There was heavy cloud obscuring the view of the Mount St Helens crater last night. Processing and enhancing the images from the Volcanocam did not reveal any signs of the incandescent glow from the lavadome.

However, simply averaging all of the volcanocam images from sunset to sunrise from last night reveals two bright spots on the images - that correspond to the two anomalous glows we have been seeing for some time now (see picture below). Further adding weight to the idea that these anomalies are caused by defective pixels in the Volcanocam camera.

I originally discounted the idea of defective pixels being the cause, due to the fact that the how spot appeared intermittently and varied in size and brightness over the course of the night and from night-to-night. However I think there is a possible explanation for this in the way the images are generated.

The Volcanocan camera is a Sanyo, Model #VCC-4594 Color CCD camera and the output is an analogue NTSC video signal - not a direct digital image from the CCD. The signal is fed to a computer where it is re-digitised and resized before being transmitted to the Volcanocam webserver. I suspect that it is the processing of the digital data to analogue video, then back to digital in the computer (and any other processing/resizing) that adds the variability to the hot pixels in the final images.

Averaging the images over the whole night, like I have done below, would help overcome any variability and we see the hotpsots for what they are - defective pixels. Of course, there's still the problem that the second hot pixel that appeared recently, did not appear on many weeks worth of images at all.

I'll go back over the archives (and produce average images like the one below) to see what happens over a longer time frame...


Monday, June 20, 2005

Looking at the site of the anomalous glow

Given the interest in the anomalous glow on the western flank of Mount St Helens, I thought it would be useful to examine the area where the glow appears to be located.

The USGS/CVO recently posted some new detailed images of the mountain which include the area where the mystery glow appears night after night. By matching the position of the anomalous glow with the daytime images it is possible to take a closer look at the apparent source of the glow.

I have matched the position of the mystery glow (circled in red) to the images from the USGS/CVO and cropped them at 100% to give the maximum amount of detail.

There does not appear to be any signs of a genuine source of volcanic activity in the area, nor is there any obvious equipment or other materials that could be the cause of a reflection causing the glow. In fact it looks like the mystery glow originates on a vertical face of the rocky outcrop in the centre of the circled area.

To my mind this adds considerable weight to the possibility that the anomalous glow is an artifact caused by some sort of defective pixel(s) in the Volcanocam camera.

I would be interested to receive any other daytime images of this region of the crater that may help answer the question one way or the other.


Credit: Edited image (cropped). Original USGS Photograph taken on June 15, 2005 by Elliot Endo


Credit: Editied image (cropped). Original USGS Photograph taken on June 19, 2005 by John Pallister

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.



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