Since developing the Paracorr (Parabola Corrector) in 1989, TeleVue have made many refinements to enhance its performance, for both visual use and imaging. By eliminating the effects of mirror-induced coma, “fast” scopes could be made as aberration-free as “slow” scopes.
TeleVue have proved that f/4 scopes equipped with the Paracorr rivaled non-corrected f/8 scopes. Shorter, more compact Dobsonians with dramatically larger fields became much more practical. Indeed, at the 2009 WSP, Mike Lockwood took it a big step forward with his 20" f/3.0, “no ladder” Dobsonian.