Paracorr for Newtonians — more stars, sharper stars, more time to observe!
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. 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.
An optical chain is as good as its weakest link. With the development of 82 degree Nagler and 100+ degree Ethos eyepieces, Tele Vue offers the largest, flattest and best corrected visual fields in the industry. Combine the Nagler/Ethos revolution, Dobsonian revolution and Paracorr for the ideal mating for spectacular wide and sharp "spacewalk" observing.
Life without Paracorr
Previous attempts to correct for coma have been limited in usefulness. Some correctors were designed mainly for astrophotography, some required difficult installation in the focuser's draw tube. Dedicated coma correcting eyepieces were another approach. However, these were limited to 50 degree apparent fields and would orphan your existing eyepiece collection.
Life with Paracorr
Paracorr is easy to use. It slips into your focuser, just like a Barlow. To minimize focuser in-travel, due to additional length, a mild 15% Barlow effect was designed into Paracorr to effectively push the focus out. Paracorr is recommended for use with all Tele Vue eyepieces because our Plössls, Radians, Panoptics, Naglers, Ethos and Delos eyepieces achieve higher levels of aberration correction than competitive models. However, Paracorr is also compatible with other eyepiece makes.
Try Paracorr on your "DobNewt." We think you'll agree that the revolution is complete.
Paracorr Eats Coma
Optimizing the Coma Correction by Using Paracorr's Tunable Top
The "Tunable Top" permits optimized aberration control for all Tele Vue eyepieces and many others, by simply loosening a screw and rotating the Tunable Top. The eyepiece barrel height raises and lowers, allowing you to maintain the proper field stop to Paracorr lens distance. For your reference, here is a recommendation guide for choosing the best setup for various Tele Vue eyepieces to get optimum correction:
Table for 3" BIG & 2" Paracorr Type-2 (VIP-3010 / VIP-2010)