The filter is now packed and ready to be shipped.
I found that I didn't use it enough for the past days, and actually, I found what attracted me most for the Sun is H-alpha. H-alpha can penetrate through (thin) cloud by overexposure, and you can get prominence at least, of course, it's not possible for surface detail and that's the case for CaK as well. With the poor Hong Kong sky and my very limited time, I would rather give it up at the time being.
The Baader CaK is very good and it has a very special property that it can be scale up very easily with your scope, and there's no other filter which can do something similar. By pushing up the aperture, there're always some surprise waiting for you to discover. Therefore, I would like someone who is more hard working to take over this. It simply wants a better home that my equipment cabinet.