There are a number of issues that can be minimized when using a Televue Powermate over a typical Barlow lens, such as vignetting, edge field aberrations and pupil movement.
Powermate's are flexible for visual and imaging with all types of telescopes and eyepieces. In essence Parfocal, and with nearly constant magnification irrespective of image distance behind top surface, with the exception of the 5x version which increases 1x for every 35mm of image distance increase.
In addition higher magnifications are possible with high optical performance when compared to "doubling up" Barlows. All will reach parfocal point in star diagonals, except for the 2", 2x which still comes very close.
Moreover full multi-coating, Powermates incorporate various other Tele Vue exceptional touches, such as safety undercuts where practical on the chrome barrel and captive lock screws that cannot fall out, and filter threads. TeleVue's 100% QC program at f/4 insures that Powermates add impressive power to your preferred eyepieces.
By way of an example, if you possess a 24mm Panoptic, you will have the power of a 12mm focal length eyepiece with the 2.0x Powermate,, 9.6mm with the 2.5x Powermate, a 6mm with the 4x Powermate, or a 4.8mm with the 5x Powermate.
Solar System Imaging with Powermates
Many of the finest Solar System images have been made with Powermates. Used singly or stacked, Powermates make it possible for any telescope to achieve the long focal-length needed to image details on Solar System bodies.
The increased image scale allows for imaging without an intervening eyepiece, like in prime focus photography. Powermate T-Ring Adapters fit on the Powermate lens assemblies to allow attachment of your camera's T-Ring or other T-threaded imaging accessory.
1¼" Powermates stand less than 3" out of your focuser, and the 5x takes 1¼" threaded filters.
They are parfocal in all 1¼" diagonals and prisms. For that reason, they're strongly recommended over typical Barlows for 1¼" diagonals and refractors such as the Tele Vue-60.
The 5x Televue Powermate is great for long focus CCD and film photography, magnifying about 7.7x.
It's an appealing, high performance alternative to eyepiece projection. The 5x is also excellent for slowing down your telescope for Hydrogen-Alpha solar observing.
2" Powermates are a better option for 2" diagonals than Barlows, because they are nearly Parfocal. They are threaded for 48mm filters and their performance is superb with every 1¼" and 2" eyepiece.
Both the 2" eyepiece holder and the special 2" flat top adapter use the Televue brass clamp rings for secure operation.
And additionally, you'll find it includes an incredibly unique feature: it is possible to unscrew the 2" eyepiece housing and screw on a special T-ring adapter for solid, compact attachment of CCD or camera equipment.
They are outstanding with long eye-relief, 2" eyepieces. Using the 4x model, consider the quality of a 35mm Panoptic at 8.8mm with 25mm of eye relief.
The Televue Powermate isn't a Barlow so the Panoptic-Barlow Interface is not necessary. The 2" Powermate fits all the way into 2" Star Diagonals, requiring minimal refocus in comparison to a 2" Barlow.
Dobsonian and Newtonian owners should note that when employing Tele Vue's Paracorr coma corrector, the 2.5x or 5x Powermate should be inserted into the Paracorr's 1¼" adapter, in between the Paracorr and eyepiece. For the 2x and 4x 2" Powermates, first insert the Powermate into the focuser, then the Paracorr into the Powermates.
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