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Carlton,
The H alpha solar absorption line when you look at the profile, is like a deep valley with wider top section. The width of the line is >2A. Beyond the wider section we move from H alpha into the solar continuum.
Simplistically, if our H alpha filter has a bandwidth of <1A then we can position it at the deepest (central section) or out in the wider sections....
The wider top sections are the "wings" of the Ha line - the blue wing towards the blue, and red the opposite.
When we observe at the Ha core (6262.8 A CWL (central wavelength)) we are looking at a region of the Chromosphere around 1500 Km above the "White light" Photosphere. As we move our filter (tuning) out into the "wings" we start to see detail lower in the Chromosphere - 200 - 300 Km above the Photosphere.
Besides the possible Doppler shift (which changes the appearance of some of the filaments - which also requires working in the wings), the wings also allow us to better see and record things like Ellerman Bombs and flares.
Hope this helps.
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