: I am considering building a Dall-Kirkham cassegrain.I have heard that an f/12 Dall-kirkaham would have coma equivalent to a f/5 newtonian. My question is; would the coma in the Dall-Kirkham be less visually perceptible because at f/12 the larger Airy-disk would mask a greater portion of the coma than the smaller Airy-disk in the f/5 Newtonian?

I built a Dall Kirkham (8 inch f15) about twenty ago The coma was not a bad as described by others. although it was mostly noticable in brighter objects. All in all I found it to be a very serviceable scope. In fact a friend of mine has been using the optics for several months and has recently added a schmidt corrector plate that has made a huge differce in its performance