Halden Redoubt 7 mm wide-field eyepiece

Specifications

Description

The Redoubt 7 mm is a seven-element wide-field eyepiece with an 82-degree apparent field and a 1.25 in barrel. Its 7 mm focal length sits at the high-power end of the range most observers use. In a 720 mm refractor it gives 103x, in a 1,200 mm Dobsonian 171x, and in a 2,032 mm Schmidt-Cassegrain 290x. At 103x, the true field in the 720 mm telescope is about 0.8 degree, enough to frame a globular cluster such as M13 with room to spare around its edges.

The field stop is 10.5 mm, which sets the true field in each telescope. Seven elements in an 82-degree design give sharp stars across most of the view in telescopes slower than about f/6. In faster Newtonians, expect some softening and field curvature toward the edge. The lenses are fully multi-coated, and the barrel is blackened to reduce internal reflections from the field stop.

With 14 mm of eye relief, the Redoubt 7 mm suits most observers without glasses and many who wear them, although a deep-set eye may need to sit close to the lens to see the full field. The fold-down rubber eyecup blocks stray light when folded up. At 230 g, the eyepiece is heavier than a standard Plössl, so check balance on small refractors and alt-azimuth mounts.

Use this eyepiece after a lower-power eyepiece has located the target. At 290x in a 2,032 mm telescope, the true field narrows to about 0.3 degree, which is useful for splitting close double stars and resolving detail in planetary disks. Pair it with a 14 mm or 25 mm eyepiece to cover three steps of magnification.

About this configuration

This listing covers one configuration of the Halden Redoubt 7 mm wide-field eyepiece, defined by its case, eyecup, finish, and edition year. This configuration comes without a case, which suits observers who keep their eyepieces in a shared foam box. No case is included, so the eyepiece ships in a simple box with its two dust caps fitted. A fold-down eyecup is simple and has no moving parts that can loosen in cold weather.

A color ring near the top of the body marks the focal length, which helps when you swap eyepieces in the dark. The optics in the 2024 edition match the other years; the changes concern the housing only. The true field in your telescope is roughly the apparent field divided by the magnification you reach with this eyepiece.

What's in the box

• Eyepiece with fold-down rubber eyecup
• Top and bottom dust caps
• Padded storage case

Compatibility notes

• Fits any 1.25 in focuser, diagonal, or Barlow lens.
• The barrel accepts standard 1.25 in filters.
• Sharp across most of the field at f/6 and slower; softer at the edge in faster Newtonians.