H-a Image Info: Canon EOS D60 digital SLR, Coronado Solarmax90/T-Max, and 30mm blocking filter
attached to a Takahashi FS128 at prime focus. Processing was done in Images Plus and final polishing in
Adobe PhotoShop.
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The underlying white-light activity may be seen by moving the cursor over the image.
This solar blink-sequence allows direct comparison of dramatic variations occurring simultaneously in the
Hydrogen-alpha and white-light bands. It is particularly interesting that while the white-light image
indicates minimal sunspot activity, the H-a components are exceedingly active.Massive filaments course
prominently above the surface, invisible to white-light and deep-density filters.

White-light filters allow us to view features of the bright portion usually thought of as the sun's "surface",
while H-a filters, rejecting all but a very narrow slice of the spectrum, allow us to see activity otherwise
overwhelmed by the intensely bright Photosphere lying below. It's not unlike the blinding light from a
high-beam headlamp which prevents seeing the faint lettering on the bulb, but an H-a filter, like a pair of
magic glasses, removes that bright background Photosphere and allows only the signal of interest to

The H-a filter used here is designed to pass a signal at 6562.8 Angstrom... the first spectral band of
Hydrogen activity, or more commonly refered to as Hydrogen-alpha. The bandwidth is also very tightly
controlled at <0.7 Angstrom, so as to provide high contrast. Moving too tightly though can diminish the
fullness of the prominences, as they tend to spill across wider frequency ranges. To put the level of
precision in perpsective, 1 angstrom is one hundred-millionth of a centimeter!

This was a collaborative effort, with Luis Carreira of Portugal providing the white-light image. You can
view the
full-scale version of the white-light image and much more on his solar imaging web-site.