Brightwell Tidewater 5 mm wide-field eyepiece, with hard case

Specifications

Description

The Tidewater 5 mm is a wide-field eyepiece with an 82-degree apparent field and a 1.25 in barrel. At this focal length it is a high-power eyepiece in most telescopes: 240x in a 1,200 mm reflector, 140x in a 700 mm refractor, and 406x in a 2,032 mm Schmidt-Cassegrain. Such magnifications suit small planetary disks, close double stars, and the dense cores of compact globular clusters, where a short focal length shows detail that longer eyepieces cannot.

The seven-element design uses multi-coated lens surfaces to reduce internal reflections across the field. Images are sharpest near the center in telescopes slower than about f/6. In faster Newtonians, the edge of the field softens, because the eyepiece must accept a wider cone of light from the primary mirror.

The 10 mm of eye relief suits most observers who do not wear glasses. Observers who wear glasses may need to place the eye close to the lens to see the full field. The 6.4 mm field stop sets the true field to about 0.31 degrees in a 1,200 mm telescope, which is enough to frame Jupiter's disk with room around it or to fit the core of a compact globular cluster.

At high power, a small true field and a dim exit pupil make tracking harder, and atmospheric steadiness limits detail. Center the target in a lower-power eyepiece first, then change to the Tidewater 5 mm once the view is steady. The eyepiece is light enough for most focusers and works well with a 2x Barlow lens when a higher magnification is needed.

About this configuration

All configurations of the Brightwell Tidewater 5 mm wide-field eyepiece share the same optical design; the options change the eyecup, the case, and the finish. The hard foam-lined case protects the eyepiece from knocks during travel and stacks neatly with other cases. A hard case keeps the eyepiece safe in a busy accessory box at a star party or an outreach event. The twist-up eyecup sets your eye at the right distance from the lens, with or without glasses.

The silver anodized body is easy to find in a dark accessory case and wipes clean after dewy nights. This is the 2023 edition of the Tidewater line, the earliest version that is still listed in the catalog. To find the magnification, divide the focal length of your telescope by the eyepiece focal length in the specifications.

What's in the box

• Eyepiece with fold-down rubber eyecup
• Top and bottom dust caps
• Cardboard storage box
• Hard foam-lined case

Compatibility notes

• Fits any 1.25 in focuser, diagonal, or Barlow lens.
• The barrel accepts standard 1.25 in filters (M28.5 x 0.6 thread).
• Sharp near the center at f/6 and slower; softer at the edge in faster Newtonians.