"This model is nearly parfocal (unlike the Big Barlow / Interface combination), so it can be effectively used in our 2"" diagonals. Its performance is excellent with every 11/4"" or 2"" eyepiece we make (yes, even the 31 Nagler Type 5!). Both the 2"" eyepiece holder and the special 2""-11/4"" low-profile adapter use brass clamp rings for secure, non-marring operation. And it also has a very unique feature: you can unscrew the 2"" eyepiece housing and screw on a special T-ring adapter for solid, compact attachment of CCD or camera equipment.|Vignetting, edge field aberrations and pupil movement - all introduced when using Barlows with long focal length eyepieces, are minimized.|Telecentric operation (field rays leave parallel to optical axis, unlike Barlow lenses which diverge rays). This is ideal for Hydrogen-alpha filter use such as with Daystar models.|High performance for image amplification, CCD or film (some of the finest Earth-based planetary imaging is being done with Powermates).|Flexible for visual and imaging with all types of telescopes and eyepieces. Essentially Parfocal, and with nearly constant magnification regardless of image distance behind top surface (except 5x model which increases 1x for every 35mm of image dista|Higher magnifications are possible with high optical performance compared to ""doubling up"" Barlows.|All will reach parfocal point in star diagonals, except for the 2"", 2x which comes very close."