Latest Version, Accepets the T-Ring Adapter 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 distance increase). These models stand less than 3in. out of your focuser and the 5x takes 1 1/4in. threaded filters. They are parfocal in ALL 1 1/4in. diagonals and prisms. For this reason, they are highly recommended over standard Barlows for 1 1/4in. diagonals and refractos such as the TeleVue-60. The 5x Powermate is ideal for long focus CCD and film photography, magnifying about 7.7x. It's an attractive, high performance alternative to eyepiece projection. The 5x is also perfect for slowing down your scope for Hydrogen-Alpha solar observing.