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Jeff, et al,
Tuning the conventional H alpha filters unfortunately is not well explained in the “manuals”. We have tilt tuned etalons and pressure tuned etalons, temperature tuning (Quark) different tuning “mechanism” which give different outcomes.
The bandwidth of the filter doesn’t change with the tuning.
The tuning moves the centreline (H alpha plus or minus some Angstrom) and allows us to observe solar features in and around the H alpha wavelength.
The issue, is knowing which way the “tuning” is moving and by how much.
With tilt etalon, the more the tilt the more the wavelength moves towards the blue.
With pressure tuning, the higher the tuning pressure the wavelength moves towards the red.
With the temperature tuning, the higher the temperature, the wavelength moves towards the blue.
Unfortunately it’s very (very) difficult to quantify the change in wavelength with the pretty coarse tuning mechanisms. (It’s much easier and far more accurate when you use a Spectroheliograph)
Obviously the details recorded in and around an H alpha feature will vary with wavelength. Activity like Ellerman bombs really needs access to the H alpha wings.
Practice, practice, practice......
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