Paracorr - more stars, sharper stars, more time to observe.

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) uses 2 multi-coated, high index doublets, is completely color-free, center and edge, and installs like a Barlow. Coma is corrected so well, the diffraction limited field area of an f/4.5 Dob/Newt is increased 36 times! - Al Nagler

PVL-2008 Visual Paracorr Note: All eyepiece interfaces have non-marring brass clamp rings.

An optical chain is as good as its weakest link. With the development of 82 degree Nagler eyepieces, Tele Vue offers the largest, flattest and best corrected visual fields in the industry. Combine the Nagler revolution, Dobsonian revolution and Paracorr for the ideal mating for spectacular wide and sharp "spacewalk" observing.

Life before 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. 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 [see performance graphs here] on all f-ratios from f/3.5 to f/8 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 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 and Ethos 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

The visual Paracorr can be used with both 2" and 1¼" eyepieces. The imaging models work with DSLR and CCD cameras (see Astrophotograpy). For visual use, slip Paracorr 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.

Visual Paracorr Parts

2" - 1¼" Adapter (ACF-2125)
Visual Paracorr (PVL-2008 ) with ACF-2125 inserted	Visual Paracorr setting marks with ACF-2125 inserted

Weight Paracorr Visual:  1.05lb
 

Optimizing the Coma Correction by Using Paracorr's Tunable Top

As you've read, all Newtonian/Dobsonian telescopes can benefit from using a Tele Vue Paracorr (Parabola Corrector) to eliminate coma in the image. One aspect to optimizing this correction is the distance of the eyepieces focus point (field stop location) to the last surface of the Paracorr lens (within a small +/- tolerance of course). Typical eyepieces used with fast Newtonians can have field stop locations differing by as much as half an inch. To accommodate for the differences, we developed the "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:

CAUTION: Do NOT use Barlow lenses with the Tunable Top Paracorr; the Barlow may contact the Paracorr lens.

Astrophotography

Mount your DSLR or CCD camera to imaging Paracorrs (see  models below), and the quality of full frame photos will be spectacular since star image sizes on film can be less than .001" over the full frame for an f/4.5 mirror. Edge-of-field sharpness is further enhanced since Paracorr also acts as a field-flattener. See our Strawberry Field fast Newtonian images.

Important Note
Paracorr is designed to work properly only with parabolic mirrors in Newtonian or Dobsonian telescopes.

You must adjust distance from last lens surface to CCD surface to 55mm ±4mm for best performance.

Paracorr to SBIG STL-series

Paracorr to STL-series (model PSB-1100)	Introducing a Paracorr designed for the SBIG STL-series astro camera. The Paracorr to STL-series (model PSB-1100) photographic Paracorr has wide threads that attach directly to the body of the STL-series cameras, placing the CCD chip at the optimum distance. For best correction, large internal lenses minimize vignetting while achieving the flat and sharp fields Paracorr is famous for with fast Newtonians. 2" barrel for standard 2" focusers.
	We are pleased to announce that the Paracorr to STL-series (model PSB-1100) is one of Sky & Telescope magazine's "Hot New Products for 2007". Paracorr to STL-series is featured in the January 2007 issue. Tele Vue is a dual-winner this year as our "is" series telescopes have also achieved "Hot New Products for 2007" status! Sky & Telescope's  "Hot Product" acknowledgement is granted to a select few of the most "intriguing" and "most noteworthy" new products every year. See more Hot Products.
	The following images by James R. Foster were taken with a fast 10" f/4.5 Newtonian and STL-series camera fitted with the PSB-1100.

Universal Paracorr

	Large field lens of the Universal is visible left. Above are some of the many IS rings available.

The extensive collection of IS adapters includes: standard T-Ring and Canon Wide T-Ring for DSLR; 2" nosepieces adapter for CCDs and direct connect adapters for select SBIG and Apogee CCDs. T-Ring adapters for DSLR need no additional spacers to achieve the standard 55mm ±4mm distance from Universal Paracorr flange to camera chip. CCD users need only to subtract the chip depth (from the camera face to chip) from 55mm to determine the correct IS spacer(s) (±4mm) to use. Universal Paracorr will accept all future IS adapters and spacers -- see the Imaging System Accessories page for a complete list.

Like all Paracorr's, the Universal fits into 2" focusers and adds 15% to telescope focal length.

User Reports

"Wow - On our 30" f/4 and 17.5" f/4.5, using 10 different eyepieces, we noted a 75% - 95% reduction in edge field coma. Paracorr is a must for anyone who owns a fast ratio telescope and enjoys wide field, deep sky viewing."
- Tom Bemus

"l begun my tests with the first quarter Moon and the 20-inch (f/3.9). Without a coma corrector there was a slight smearing of lunar detail away from the center of the field. It looked like the focus needed to be 'tweaked,' but, of course, doing this did not improve the view. With the Paracorr the entire disk of the Moon appeared in sharp relief."
- Sky & Telescope Magazine

"I met up with Al Nagler who was showing off the new 31mm Type 5 Nagler and the prototype adjustable Paracorr - good thing I had my credit card with me... the views in the 31[mm]/Paracorr combo are absolutely stunning. Stars in the Double Cluster are pinpoint to the edge. The true field is almost a full degree. Eta Carina fills the eyepiece with it's detailed nebulosity. The colors of the Orion Nebula are vivid, the entire loop and M43 are easy in this richest field combo. Andromeda's dark lanes sweep across the field of view and M32 floats comfortably nearby. A simple twist on the adjustable Paracorr optimizes it for my 9mm Type 1 Nagler, and moments later we're deep into the Trapezium with countless tiny pinpoints stars embedded throughout the central nebula. Uncle Al has outdone himself again (how does he keep doing it?) . On the new 22 StarMaster, this is the ultimate richest field eyepiece combo. For you Monty Python fans, the Holy Hand Grenade is here at last - it's made by Tele Vue."
- Vic & Lynne Menard, published in Amateur Astronomy Magazine

Product List & Code

Paracorr
PVL-2008			Paracorr VISUAL, with Tunable Top
VIP-2010			Paracorr Type 2
PSB-1100			Paracorr to SBIG STL-series
PLU-1106			Universal Paracorr
PTT-2002			Tunable Top for discontinued PLA-2001

See this section on our new website.