Concept: I have built Newtonian reflectors since my high school days and still enjoy observing with Dobsonians. Knowing how the Nagler eyepiece complemented fast Dobsonians and Newtonians by removing eyepiece induced astigmatism, I now became intolerant of the inherent defect of coma in a parabolic mirror.
Paracorr — more stars, sharper stars, more time to observe.
In 1989 I decided to try to achieve the same field quality for parabolas as reached by my Nagler eyepiece and 4-element refractor designs. Existing coma correctors seemed to be limited in color correction, spherical aberration and convenience in use. Paracorr (parabola corrector) is completely color-free, center and edge, and installs like a Barlow. In 2009, we decided to greatly improve the correction with the Paracorr Type-2 design (followed by 3" BIG Paracorr Type-2 in 2014) so that new, large, Dobs as fast as f/3 could become practical. Ladderless Dobs with larger fields herald a revolution. Read the reviews and story, The New Dobsonian Revolution, in Astronomy magazine. The new Paracorr Type-2 is a combination visual and imaging system designed by Paul Dellechiaie and our staff. Let the revolution begin. — Al Nagler
Ladderless Dobs with larger fields herald a revolution. Read the reviews and story, The New Dobsonian Revolution, in Astronomy magazine.•2" Paracorr Type 2 Instructions •3" BIG Paracorr Type 2 Instructions
•Chart (JPG): Spot Size Graphs