For a newtonian telescope with an f/5 or shorter focal ratio, the Paracorr is essential.  Edge-of-field stars that are as sharp as the stars in the center down to f/3.5 and below. Faint stars in the outer field pop out and planets that drift across the field stay focused.  Incl. 1.25" adapter.

• Specifications
• VIP-2010 Paracorr Type 2 weight 1.1 lbs.
• barrel fits 2" focusers
• eyepieces accepted 2" or 1¼"
• (includes 1¼" adapter)
• mag. (Barlow) effect 1.15x
• Threaded for 2" filters

From Al Nagler:
I have built Newtonian reflectors since my high school days and still enjoy observing with Dobsonians. Knowing how the Nagler eyepieces complemented fast Dobsonians and Newtonians by removing eyepiece induced astigmatism, I now became intolerant of the inherent defect of coma in a paraboloidal 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 eyepieces 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 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

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 paraboloidal 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 Type-2
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 into your focuser like a Barlow lens, and your eyepiece into Paracorr. 1¼" eyepieces will make use of Paracorr's special 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.

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.

Here is the easy way to dial in the best coma correction for each eyepiece:
Let's review how to set the Paracorr when you don't know the correct setting and you have no TeleVue eyepieces (if you have a TeleVue eyepiece, use their prescribed setting for that eyepiece and all the other eyepieces will follow--instructions follow:)

Start with the out-most setting of the Paracorr. Focus the telescope and examine the edge of field stars. Still see coma? Move the Paracorr in one setting and refocus. Still see coma, but it's improved? Continue in one more setting.
With trial and error, you will find one setting that produces the least coma at the edge of the field. If aberrations are not fully corrected, it's likely the eyepiece has some residual astigmatism at the edge of the field that the Paracorr won't correct.

Once you have the proper setting for that eyepiece, write it down so you can return the Paracorr to that setting before using that eyepiece the next time.

Now, how to set the other eyepieces once you have a perfect setting for that one eyepiece:
Put the second eyepiece in and focus using the tunable top of the Paracorr (don't use the focuser's knob(s)). When that eyepiece is in focus, look at the tunable top setting. That will be the setting for that eyepiece. Write it down so you can go to that setting before the next use of that eyepiece.

In that manner, you can do an entire collection of eyepieces without knowing in advance what the settings for those eyepieces are.

As you can see, the tunable top makes all your eyepieces parfocal--only the movement in and out of the tunable top before you insert the next eyepiece is required, plus, perhaps, a tiny bit of refocusing. But the movement of the focuser will be tiny as long as the Paracorr is used.

What if you cannot correct the coma of an eyepiece because the Paracorr's settings don't extend far enough to fully correct that eyepiece?
Well, that's not unusual. The 31 Nagler and 21 Ethos were in that category on the original Paracorr. And the 17.3 and 14 Delos are in that category on the Paracorr II (though the amount is very tiny and the coma correction *almost* perfect).
Don't worry about it. If the eyepiece is close to the ideal coma correction setting the images will still be improved significantly over no Paracorr at all.
BUT, don't use THAT eyepiece to determine the settings for your collection. Use an eyepiece that has its best coma correction among the settings of the Paracorr. And, to make sure you have a good starting point, use your eyepiece that has the widest apparent field of view because coma will be more visible in that eyepiece than in narrower field eyepieces.

After you have determined the correct settings for all your eyepieces, even those whose correction is not ideal at one extreme or the other of the Paracorr settings, hopefully you will have written down the settings. If, like me, you don't want to resort to a list before inserting the eyepiece, use a label maker to put the Paracorr setting on the side of the eyepiece so you don't have to remember.

There is an alternative to this, and I admit to using it when I'm using an eyepiece briefly and then inserting another eyepiece: Having the setting absolutely perfect for one eyepiece, I insert another and simply focus using the tunable top. Then, I touch up the focus a tad with the main focuser. That way, I don't even have to read the label on the eyepiece to find the correct setting for the next eyepiece. It's a little less effort if you have eyepieces that all use extreme settings (most of mine use one extreme or the other) and your less-often-used eyepieces use an intermediate setting.

TeleVue eyepieces, Barlows, PowerMates, and Paracorr are warranted to be free from manufacturing and workmanship defects for lifetime from the date of purchase.  This warranty applies to the original purchaser and is not transferable.  Defects covered under this warranty are limited to optical coating and cementing, and normal mechanical operation of the product.  The warranty does not include damage caused by mishandling, alteration, normal wear and tear from use, defects of a subjective nature, or coverage for any product not purchased through an authorized TeleVue dealer.
The original owner must complete a warranty registration card and send it to TeleVue Optics for the warranty to be valid, unless state law supersedes.  In such case, or if warranty cards are not submitted, an original dated sales receipt containing the original purchaser's name will serve as proof of purchase for registration.
If your TeleVue eyepiece, Barlow, PowerMate, or Paracorr requires warranty service, please call TeleVue at (845)469-4551 to discuss the problem and obtain a return authorization.  No returns are accepted without prior authorization.
Warranty work will be performed at TeleVue's discretion and may ONLY be performed by TeleVue Optics.  Warranty is void if work is performed on your product by anyone other than TeleVue Optics.  TeleVue Optics reserves the right to assign warranty service to Authorized Service Centers.  In the event a product cannot be serviced, TeleVue will replace the defective product with a current equivalent.  All shipping and insurance charges are excluded from this warranty.
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