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Staring at the sun

Astrophotographer Alan Friedman has captured remarkable images of the sun from his backyard in Buffalo, New York, using a Point Grey FireWire camera.

By imaging with a streaming camera, Friedman was able to record brief moments of clarity that come in the midst of otherwise poor imaging conditions. These frames would be virtually impossible to capture using a traditional camera shutter. His imaging technique involves scanning the captured video, selecting (both manually and with software) the sharp frames and then aligning and averaging them to yield a summed image of only the best information from the original data.

The Scorpion IEEE 1394 monochrome camera, featuring a Sony 1/1.8-inch CCD, streams 1,600 x 1,200 images at 15fps, and offers 20 times the dynamic range of a DMK camera. This range allows the camera to record surface structures in the solar chromosphere, as well as much dimmer prominences at the edge of the sun in the same exposure. The ability to set a Region of Interest (ROI) is another great tool for maximising the download speed of the camera when the full field is not needed.

In two separate 90-second videos, Friedman zoomed in on the edge of the solar disk to capture wisps of gas arcing along loops of the sun's magnetic field, plus sunspots and the detailed churning of the sun's atmosphere. Then he inverted the solar disk in the image, making all the dark spots light and the light spots dark. This technique, he says, brings out the surface detail in high contrast and provides a smooth transition from the disk to the edge prominences that is closer to what one might experience visually looking through a safely filtered solar telescope.

'It gives a sense of the sun that's both powerful and closer to what you would actually see,' Friedman said.


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