That's not a knife. THIS is a kn... I mean CA.
Taken with the infamous Long Perng ED90 doublet.
Be sure too your camera settings don't contribute to it. At first I thought my SW ED100 F9 had CA, but it was actually a setting in the camera that was causing it. Since I sorted that out, CA isn't an issue. Flare on the other hand....
I'm not familiar with that model of WO scope, but I have read that some of the doublets do have a little residual CA. If you push them hard enough, most refractors will show it. If it's minor CA like yours, a fringe killer will deal with it, as will a Semi-Apo filter. The Semi-Apo is a good filter for nebula as well.