THIS PAST YEAR, Tele Vue introduced the Paracorr Type 2, a new version of its original Paracorr, an accessory that counters the effects of coma inherent in Newtonian reflectors with "fast" focal lengths (f/5 and shorter). I selected two targets as test objects, Andromeda Galaxy (M31) and the Double Cluster, both of which are large enough to fill the field of view in my 12.5-inch PortaBall Newtonian.
Using a 17mm Ethos, I initially looked at M31 with the eyepiece alone. I am always captivated at the beauty of this object an enjoy trying to discern as much detail in the faint dust lanes as possible. And, as usual, I was quite happy with the view. Upon inserting the new Paracorr Type 2, I was immediately shocked at how much sharper and more detailed the view was! The stars were much more tightly defined along the edge of the field of view. I admit that it takes a lot to surprise me after so many years observing with this scope, but this certainly did.
I experienced the same effect while viewing the Double Cluster. After switching back and forth multiple times with and without Paracorr Type 2, there was no doubt in my mind that the views were much improved.
Tele Vue's website states that the Paracorr Type 2 is designed for reflectors with focal ratio of f/4.5 or faster and that anyone with a slower reflector should use the original Paracorr. My Newtonian is f/4.8, and I certainly experienced a definite increase in sharpness with the Type 2.
The Paracorr adds 15 percent to the magnification of the eyepiece used. Simply insert the Paracorr into your telescope's 2-inch focuser (the Paracorr itself is able to accommodate both 2-inch and 1.25-inch eyepieces), insert your eyepiece, and then adjust the Paracorr to the recommended setting. Tele Vue provides a chart with the correct settings for its eyepieces. Other manufacturers' eyepieces can be used in the Paracorr, but you will have to determine the correct settings yourself or find them online. With the Paracorr's size and weight (1.1. lb.), you will want to make sure that both your eyepiece and the Paracorr are well secured to each other and that the Paracorr is firmly seated into your telescope's focuser The Paracorr Type 2 can be used both visually and photographically.
— Carlson, T. "Improve the View with Paracorr Type 2". SkyNews, (May/June 2011). Reprinted with permission. © 2011 SkyNews Inc. All rights reserved.