"While Barlows are powerful tools, the negative element defining them also limits their ability. The simple negative element Barlow increases eyepiece eye-relief. With short focal length eyepieces the effect is negligible. However, on long focal length eyepieces the exit pupil position moves well beyond the designer's intended position, resulting in vignetting with many eyepieces. This is why "Shorty" Barlows in particular, with their strong negative element often vignette and degrade long focus eyepieces. My 4-element form picks up where the Barlow concept can go no further. Powermate is a technically universal solution, using a positive field lens to redirect field rays. The result is an exit pupil that stays where the eyepiece designer intended. With freedom from aberrations, greater magnification potential, and compact size, I hope you'll agree Powermate raises the standard for image amplification." - Al Nagler
Pump up the power with Tele Vue Powermates. Powermates are ideally compatible with all eyepiece types, are optically "invisible" in the image, and are the best choice for photography when you want a larger image scale. They truly go where no Barlow has gone before.
Of course, Tele Vue touches such as full multi-coating, captive lock screw with brass clamp ring, complete baffling, and 100% quality control at f/4 ensure your satisfaction.
Tele Vue 2" Powermate in 4x Magnification
You can use this 4x Powermate to gain higher powers with typically long focal length 2" eyepieces. This Powermate requires far less refocussing compared to 2" Barlows when used in star diagonals. Weight = 1.20 lbs.
In addition to full multi-coating, Powermates include other Tele Vue special touches such as safety undercuts where practical on the chrome barrel, captive lock screws that can't fall out, and filter threads. Their 100% QC program at f/4 insures that Powermates will add dramatic power (and NOTHING ELSE) to your favorite eyepieces.
Powermates are the easiest method of increasing focal length for CCD and film photography. Each has been designed to accept optional adapters with T-ring threads. It's an attractive, high performance alternative to eyepiece projection.