Today saw "first light" for the f/40 refractor. This is just an experiment and not a serious telescope, but I had to try it before building the f/20. I mounted a 50mm singlet that, after subtracting a tad for mounting purposes, comes out to a clear aperture of 47.6mm, yielding a final f-ratio of about f/42. I can see why Huygens, Cassini, and others of their time used singlets upwards of f/200. F/40 is too short to suppress the chromatic abberation sufficiently for reasonably sharp imagery with a non-achromatic lens. Everything is surrounded by a rainbow of color, at least on daytime objects. I will use it on the moon tonight and perhaps Jupiter but I'm not expecting much. I'm getting 50X with a 40mm eyepiece and don't want to push it much higher than that. I tried a 12mm Kellner and that clearly pushed the magnification well past the diffraction limit (166X). There was no recognizable image at all. Another thing I noticed was the depth of field. You could rack the drawtube half an inch with very little change in image sharpness. Maybe wearing a powdered wig and buckled shoes will improve the view with the f/40, but I'm not going to try! *;o)* I will post images as soon as I can access my Gallery pages. This scope is nearly 7 feet long and quite impressive even though the main tube is only 2" OD. And I still had to use 2 extension tubes to reach focus- the aluminum tube I had on-hand was about 8 inches too short! The next step is the telescope's final configuration, the F/20 project. I will be using an old Jaegers 50mm achromatic objective of known good quality. The clear aperture should be a true 50mm with this one. The F/20 project is a telescope that I have wanted to build for decades. It is essentially the one designed by Sam Brown on page 128 of the 1967 edition of "All About Telescopes". A 2" achromatic refractor of 50" focal length. Mine will be 10" shorter than Browns, due to his being an f/25. The Edmund lens (no longer made) was air-spaced, the Jaegers is cemented. I am also using a 2" OD tube for compactness; Brown used a 3" OD aluminum tube. I haven't decided yet if I will line the tube with flocked paper or build a baffle tree. 2" is a mighty small tube to work with when one is accustomed to something you can stick your head into. I've seen many objects with 70mm and 80mm refractors and am now ready for the 50mm (2-inch!) challenge. I think many of you would be surprised at the remarkable views you can get with a small aperture. Stay tuned, photos uploaded when I can access the Gallery.