I have been told that some of the criteria to evaluate optics quality by comparing the inside out of focus image to the outside out of focus image does not apply to refractors. However, it seems some of it should apply. Assume the outside out of focus image looks very good and circular and looks like the text book example of good optics in Star Testing Astronomical Telescopes, by Suiter, pages 12 and 13. Assume the inside out of focus image also looks the same (circular and like the text book example), but it is reduced in brightness and tends to sometimes be difficult, depending on the star color, to see because of atmospheric turbulence. For some star colors the atmospheric turbulence is not very evident and the the two images look almost identical. Is this still evidence of good APO optics, even though the inner out of focus image is not exactly identical (i.e., dimmer) to the outer image, and it seems to be more prone to atmospheric turbulence? Stan -- See message header for info on list archives or unsubscribing, and please send personal replies to the author, not the list.