Propagation velocities of gas rings in collisional ring galaxies

We report laboratory results from a monochromatic prototype of the Phase Knife Coronagraph which validate our previous theoretical and numerical simulations, prove the physical principle of it and set realistic limitations to the nulling properties of the coronagraph. The optical set-up, phase knife manufacturing technique and different aspects of the instrumental limitations are given. The first results attain easily a 3000 nulling effect obtained both on single and simulated double stars. Optical and mechanical stabilities are discussed and future steps to be carried out for a wide band version of this coronagraph are outlined.