Coma Correction

Now you can eliminate Coma when you use your Tele Vue Eyepieces with a Newtonian Telescope

What is Coma?

Coma makes stars look like blurry comets whose tails point out radially from the centre of the field. The faster your scope's speed, that is the shorter the focal length, 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.

Tele Vue Visual Paracorr TeleVue Paracorr is a universal corrector that tightens and intensifies star images on all f-ratios from f/3.5 to f/8 without adding any false colour 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 recommended for use with all Tele Vue eyepieces that you may use with a Newtonian telescope, because our Plossls, Radians, Panoptics, and Naglers achieve higher levels of aberration correction than competitive models. However, Paracorr is also compatible with other eyepiece.

Paracorr Eats Coma

The Paracorr can be used with both 2" and 1¼" eyepieces, as well as with your 35mm camera body. For visual use, slip Paracorr into your focuser like a Barlow lens, and your eyepiece into Paracorr. 1 1/4" eyepieces will make use of Paracorr's special low profile 1 1/4" reducing adapter. Paracorr is threaded for 2" filters.


Tele Vue Visual Paracorr (PCV-2000) is for primarily visual use and comes with the 2" - 1¼" Adapter(ACF-2125) However, it can be used for CCD nosepieces having 2" or 1¼" diameters, like eyepieces. You must adjust distance from last lens surface to CCD surface to 55mm +4mm for best performance.
Visual Paracorr - Front View Visual Paracorr - Back View
Front View of the Visual Paracorr Back View of the Visual Paracorr showing the marks on the Tunable Top (see below for more information)


OPTIMIZING YOUR TELE VUE NAGLER TYPE 4 AND TYPE 5 EYEPIECES WHEN USING PARACORR'S TUNABLE TOP

All Newtonian/Dobsonian telescopes can benefit from using a Tele Vue Paracorr (Parabola Corrector) to eliminate coma in the image. One aspect to optimising 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 optimised 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: Recommended Eyepiece Position Chart - Setting Marks

Recommended Eyepiece Position Chart - Setting Marks
Mark 1 Mark 3 Mark 4 Mark 5 Mark 5
2" Eyepieces 2" Eyepieces 1¼" Eyepieces 2" Eyepieces 1¼" Eyepieces
20mm Nagler T2 26mm Nagler T5 All Radians 31mm Nagler T5 16mm Nagler T2**
20mm Nagler T5 17mm Nagler T4 All Plossls through 32mm 22mm Nagler T4 12mm Nagler T2**

13mm Nagler*
(original)

   All 1¼ only Naglers
(original, T5 & T6)		   12mm Nagler T4**
41mm Panoptic   24mm Panoptic   9mm Nagler**
(original)
35mm Panoptic   19mm Panoptic    
27mm Panoptic   15mm Panoptic    
22mm Panoptic*   All Tele Vue Zooms    
  * Use only in 2" mode as listed for best correction
** Use only in 1¼" mode as listed for best correction

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

Tele Vue Photo Paracorr
2"- 1¼" Adapter (ACF-2125) 2"- 1¼" Adapter (ACF-2125)
(For older tunable tops or and Visual Paracorr with slot the adapter needed is the PRA-2003)
Paracorr Tunable Top (PTT-2002) Paracorr Tunable Top (PTT-2002)
Paracorr Photo Lens (PLA-2001) Paracorr Photo Lens (PLA-2001) with the thread for 35mm cameras visible at the top


Mount your 35mm SLR to Paracorr, 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.

The photo model has T-Ring threads so that a 35mm camera body with T-Rings is properly positioned. If a CCD is used, set path length from Paracorr flange surface to CCD surface to 55mm +4mm for best results.