This is side by side comparison of two telescopes I built. One is a standard Newtonian that I made 10 years ago. The other is a Lurie-Houghton Newtonian that I just finished. Both are 6 f/4.5 so a direct side by side comparison can be made. A Lurie-Houghton Newtonian uses a two element corrector. All optical surfaces including the primary mirror are spherical. The benefit is that there is no off axis coma, the focal plane is much flatter, and that there are no diffraction spikes since no spider is needed. The optics on the Lurie-Houghton were uncoated so a much dimmer star was used for the standard Newtonian. The exposures adjusted slightly from ~ 1s so that the light levels were equal. As you can see, the Lurie-Houghton has a much more symmtric star image off axis and the astigmatism is only detectable very close to focus. In fact the off axis and on axis sequences are almost identical. I cant wait to get the optics coated and take some pictures!