David,
Thanks!
The ZWO tilter is ideal for removing Newton Rings but not for dynamic narrow band filter tilting.
I'm lucky enough to have a couple of SkyBender filter tilters. These units allow a full degree of freedom and are pretty repeatable.
To be honest, it really needs the spectrograph, with resolution around 0.05A to accurately determine the CWL and and bandwidth.
The differences between H alpha and CaK are shown below.
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