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Paracorr Telescope Accessories > Paracorr > Visual Use
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:

Table for 3" BIG & 2" Paracorr Type-2 (VIP-3010/2010)
Position A B C D E F G H
2" Oculars
(Dist. from Ref.)
-0.4" -0.3" -0.2" -0.1" 0" +0.1" +0.2" +0.3"
Panoptic 35 41 & 27
Nagler Type 4 22 17  
Nagler Type 5 31 26 20  
Nagler Type 6  
Nagler Zooms  
Ethos 21 & 17 13, 10,
3.7SX & 4.7SX
(w/2" adapt.)
1¼" Oculars
(Dist. from Ref.)
0" +0.1" +0.2" +0.3" +0.4" +0.5" +0.6" +0.7"
  32-to-8 40
Radian all
DeLite all
Panoptic 24 & 19
Delos 17.3 & 14 12-to-3.5
17.3* & 14*
Nagler Type 4 12
Nagler Type 5 16
Nagler Type 6 all
Nagler Zooms 2-4 & 3-6
Ethos 8 & 6 3.7SX & 4.7SX
*Use at "D" with AIT-2125 In-Travel Adapter.
All eyepiece interfa...
All eyepiece interfaces have non-marring brass clamp rings.

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