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 Astronomymagazine. 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

Paracorr

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

Coma makes stars look like blurry comets whose tails point out radially from the center of the field. The faster your scope's speed, the worse the effect. All parabolic mirrors used in Newtonian reflecting telescopes are limited in field sharpness due to coma. Even a perfectly made 13" f/4.5 parabola has only about 0.1 degree diffraction limited field.

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 a universal corrector that tightens and intensifies star images on all f-ratios down to f/3! Without adding any false color or spherical aberration! You no longer have to constantly shift a Dobsonian to keep objects centered for sharp viewing. Using a Tele Vue eyepiece, put M-13 at the edge of the field and enjoy fully resolving its beauty as it drifts across your view.

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

Paracorr can be used with both 2" and 1¼" eyepieces. For visual use, slip Paracorr Type-2 into your focuser like a Barlow lens, and your eyepiece into Paracorr. 1¼" eyepieces will make use of Paracorr's special low profile 1¼" reducing adapter. Paracorr is threaded for 2" filters.

SIPS

Note: The Paracorr Type 2 optical assembly is also available in a special adapter housing made by Starlight Instruments for their Feather Touch focusers. This unit avoids the need for a tunable top to optimize eyepiece position. Some Dobsonian manufacturers may also offer the Feather Touch focuser with integrated Paracorr type 2 as standard. Starlight Instruments offers Paracorr Type 2 integrated with Feather Touch focuser or as an add-on if you already have a Feather Touch focuser.

Astrophotography

Paracorr also works with DSLR and CCD cameras. Just unscrew the lens assembly from the Tunable Top and attach appropriate threaded accessory tubes and camera mounts. See 2" Imaging (Paracorr Type-2).

BIG Paracorr Type-2 for 3" Focusers

Tele Vue's 3" BIG Paracorr Type-2, designed by Paul Dellechiaie, extends the Paracorr type 2's optical benefits for imaging applications by amateurs and professionals using CCD formats as large as 52mm diagonal and paraboloids as fast as f/3. Back focal length has been extended to 80mm to allow for additional accessories to be placed in the optical path. The 5.1" length optical assembly is topped with a "stop" flange having 3.40"-24 pitch threads to mount camera adapters and spacer tubes (available later).