Tele Vue 4x Powermate - 2"

The Powermate Concept: A 4-Element Pupillary Corrector

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 the 4-element answer: 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.

4x Magnification with Long Eye Relief Eyepieces

Al Nagler's guide suggests choosing a long focal length eyepiece with comfortable eye relief and using image amplifiers to increase power.

For example, pairing the 4x Powermate with a Tele Vue 22mm Panoptic eyepiece creates the optical equivalent of a 5.5mm eyepiece. Check the result against your telescope: aim for at least 150x for planets and double stars, with about 300x as the usual atmospheric limit. A 5.5mm equivalent gives 109x in a TV-85 (600mm), 218x at 1200mm and 369x in an 8" SCT of 2032mm.

Imaging

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

• Planetary Imaging: For the 2" 4X Powermate, unscrew the top half of the black barrel and thread on the 4X T-Ring adapter, then attach your camera's T-ring.
• Balance: Heavy 2" eyepieces with the 2x or 4x Powermate could make proper balance difficult on smaller instruments.

Mechanical Integrity: A 2-Inch Barrel with Brass Clamp Ring

Powermates have a safety undercut on the chrome barrel where practical, and captive lock screws that can't fall out.

The spec table lists a brass clamp ring eyepiece holder and 2" filter threads.

Use with Newtonian Reflectors: Integrating the 4x Powermate and Paracorr

The Powermate also works with Tele Vue's Paracorr coma corrector in Newtonians and Dobsonians.

To use the 2-inch 4x Powermate with a Paracorr, you first insert the Powermate into the telescope's 2-inch focuser. Then, you insert the Paracorr directly into the top of the Powermate.

The Powermate Family: Choosing the Right Magnification

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

• vs. 2x Powermate: Half the power, also 2", with 48mm filter threads. In long focal length telescopes the 2x keeps more combinations under 300x.
• vs. Tele Vue Barlows: The Powermate goes beyond the simple Barlow concept to give a compact, high power, fully corrected image amplifier. Tele Vue also makes 2-element Barlows.

The atmosphere usually limits planetary observing to about 300x, no matter how large the aperture, so the 4x suits shorter telescopes, longer eyepieces or imaging.