All frames taken with the lens wide open and using autofocus, typically best frame out of three. A previous test showed that the autofocus was at least as good as manual focus with the Angle Finder C set at 2.5x magnification. With the extenders (2x and stacked 1.4x + 2x) it was often necessary to first focus manually to get the lens very close, and then click the autofocus. Click "original" below to see the crops at 560mm at 1:1, the other crops are then maginfied beyond 1:1. The (enlarged) frames were first composited together and then all were sharpened in one go. From the haze on the right limb of the Moon it is obvious that air transparency was less than ideal, even though the sky looked quite clear. My conclusion? No point in using stacked extenders with this lens. The aperture becomes too slow for astro use and improvement in resolving detail is hardly apparent. Your conclusions...? Examples using this lens on DSOs (Deep Sky Objects) follow next.