Self-made collimation tool. This is a kind of Cheshire tube but with internal illumination by a white LED. The black cap has a tiny hole drilled on the center. The lenght of the tube is selected to match my telescope so that the secondary mirror can also be collimated.
At lower right is a photo of the view when collimating the scope. When the inner black ring does not touch the outer black ring, collimation is ok. The outer black ring is on the inside of the black cap and the inner one is the center dot on telescopes main mirror. I had to add one on the mirror since my 150mm f5 GSO did not have one. When viewed by an eye this image appears very clear and sharp unlike on this photo.