Tele Vue 5x Powermate - 1.25"

The Powermate Concept

Barlow lenses have negative power that diverges field rays; made too short or with too much magnification, they can cause severe vignetting and image degradation from mismatched pupils. The Powermate is a 4-element parfocal, compact amplifying lens system: a negative achromatic doublet plus a positive "pupil-correcting" doublet.

Your eyepiece will operate with pupil locations where the designer intended, and no additional "interface lens" is needed since Powermates have it built in. Other features are full multi-coating, captive lock screws that can't fall out, and a 100% QC program at f/4.

A 5x Magnification Factor: From a 22mm Panoptic to a 4.4mm

Al Nagler's guide suggests choosing a long focal length eyepiece with comfortable eye relief and using image amplifiers to increase power, and his manual note says Barlows retain eye relief.

For example, when paired with the 5x Powermate, a Tele Vue 22mm Panoptic eyepiece performs like a 4.4mm eyepiece. This principle applies across your collection:

• 32mm Plössl: acts like a 6.4mm.
• 24mm Panoptic: acts like a 4.8mm.
• 17.3mm Delos: acts like a 3.5mm.

Visual Observing and the 300x Limit

Aim for at least 150x for planetary and double star observing, no more than 60x per inch of aperture for scopes up to 6", and about 300x as the usual atmospheric limit whatever the aperture. With 5x, that ceiling arrives quickly: in a TV-85 (600mm) a 22mm eyepiece gives 136x and a 13mm gives 231x.

At these powers exit pupils are small; at 1mm or less you probably will not need eyeglasses.

Planetary Imaging: The PTR-1250 T-Ring Adapter Connection

Powermates are ideal alternatives to "eyepiece projection" for photography and CCD imaging.

To create a rigid, secure imaging train, the 5x Powermate connects directly to your camera's T-ring using the optional Tele Vue PTR-1250 T-Ring Adapter. Unscrew the bottom portion of the black barrel, thread it onto the Powermate 1.25" T-Ring adapter, and screw that into your camera's T-ring adapter.

Mechanical Details: A 1.25" Barrel with Brass Clamp Ring

The 2.5x and 5x Powermates are threaded for 1¼" filters. The spec table lists a brass clamp ring eyepiece holder and a 1.6" (41 mm) maximum barrel diameter, and the box holds top and bottom dust caps.

Both 1¼" Powermates are parfocal with the Tele Vue 1¼" 90° diagonal, often used in smaller telescopes. With a Tele Vue Paracorr in a Newtonian or Dobsonian, insert the 1¼" Powermate into the Paracorr's 2"-1¼" adapter and set the Tunable Top at its highest position.

The 5x Powermate vs. the 2.5x and 4x Models

Tele Vue makes Powermates in 1¼" (2.5x and 5x) and 2" (2x and 4x). With a 22mm Panoptic they give 8.8mm, 4.4mm, 11mm and 5.5mm.

• vs. 2.5x Powermate (1.25"): Half the power, same barrel, filter thread and diagonal parfocality. In long focal length telescopes it keeps more combinations under 300x.
• vs. 4x Powermate (2"): A 2" model that takes 2" eyepieces, and 1¼" ones with its adapter. The 5x takes 1¼" eyepieces and weighs 181 g.