This is an interesting topic. Yes, deringing acts on the whole image now. Which actually means that
deringing works now 
I can then eliminate the black rings around the stars.
Unfortunately, this eliminates most of the wavelet sharpening too.
Indeed sharpening *is* ringing. Without some ringing, there is no edge enhancement at all. Now the problem is that all of us love ringing on certain parts of the image, but hate it on others. Our perception of ringing is purely subjective
You know what I mean: ringing is OK on those nice nebular features, but is absolutely objectionable around stars. Unfortunately, the Gibbs effect knows nothing about human preferences and is of course implacable: ringing originates around every jump discontinuity in the image.
The new deringing algorithm is very efficient, but it requires a very accurate adjustment most times. You may need to fine tune the dark-edges threshold up to two or three decimals. For deep sky images, you normally don't need bright-edges deringing, so leave it at its default zero value. The key is to find the precise point where ringing is practically eliminated around small and bright objects (stars). It's a matter of finding the best compromise, and as always each image is a different story. Indeed, a star mask can be of great help in most cases. With a good mask, you can tolerate more ringing (and hence more detail enhancement) because the mask will protect sensitive areas.
If you show us the image we can try to help you. And of course, the next series of video tutorials will show this and many more new features and tools available in PI 1.5.
