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

5 Comments:

Anonymous Anonymous said...

Doesn't the area that is dark immediately surrounding the red circle appear to be chunky lava flow? It doesn't look smooth like the regular crater walls.

2005-06-21, 7:32 AM  
Anonymous Anonymous said...

Wouldn't it make sense for the Forest Service to move the camera angle slightly, to see if the glow changes position relative to the mountain, or remains in the same position?

2005-06-21, 8:58 AM  
Blogger Daz said...

The area doesn't look smooth to me at all, that's why I don't see how it could be reflecting light from elsewhere. Maybe when it was covered in snow and ice, but that has obviously all melted now...

Moving the camera or adjusting the focal length slightly woul be the easiest way to settle the matter. I'm sure that over the coming weeks the camera will need a tweak anyway and the US Forest Service folks will do this. Then we'll all know for sure whether its a problem with the camera or something else!

2005-06-21, 6:51 PM  
Anonymous Bob Harrington said...

My problem with the 'glow' being an actual artifact on the mountain is that it is the ~only~ thing that approaches being focused in the nighttime images after the camera defocuses as light levels fall.

If it is something more than an electronic artifact, I would be looking for a dim lightsource reflecting in the window the camera looks through - for example, an LED on a computer in the room, perhaps?

And perhaps someday the camera could be set to manual focus and left at infinity so it wouldn't defocus each night. Though we would lose the nice macro raindrop images on our more typical gray days... ;^)

2005-06-23, 5:39 PM  
Blogger Daz said...

It can't be a reflected light from inside a room as the Volcanocam is in a weatherproof housing under cover on the outside of the building at JRO.

As far as I know the lens is a manual focus lens (Tamron 5-50 mm), as at least one time they adjusted the zoom they had to go back a couple of days later to adjust the focus.

The main thing that effects the images at night is that the camera automatically removes the near-IR filter from the lightpath when the light level drops below 0.6 lux and switches to b&w mode, which increases the sensitivity to 0.03 lux. The increased gain also results in the increased noise level that we see in the images.

I'm not all that surprised that the hotspot appears in focus, as if it is caused by a hot pixel in the CCD , then it should always be a sharp dot.

The CCD is 768x494 pixels (effective) in dimensions, so it seems reasonable to me that in the process of converting the image from digital to an analogue tv signal, then re-digitising it and resizing to 640x480 that some variation will occur in the final images we see on the web. Hence the variation in the brightness of the hot spot we see through the night.

that's my best guess at the moment anyway... :-)

2005-06-23, 8:57 PM  

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