Has anyone made a real Serrurier design, where there is a bottom truss that is designed to sag as much as the top so there is no angular shift of the secondary and focuser from the optical axis? Most ATM designs have only the top set of poles set in a solid and more rigid bottom box. Is this just half of a Serrurier? Once you get to decent poles, say 1.25 aluminum, is the nonsymmetrical sag small enough not to matter?
Aart M. Olsen aart@uiuc.edu 217-333-7467 College of Veterinary Medicine Univ of Illinois at Urbana-Champaign