Halden Strider 40 mm wide-field eyepiece

Specifications

Description

The Strider 40 mm is a six-element wide-field eyepiece with a 70-degree apparent field and a 2 in barrel. Its 46 mm field stop is close to the largest that a 2 in barrel allows, so it shows the widest true field a 2 in telescope can give.

In a 1,200 mm Dobsonian, the Strider 40 mm gives 30x and a true field of about 2.2 degrees. That is enough to see the whole Andromeda Galaxy with its companions, the entire Veil Nebula complex with a filter, and the full sweep of the Double Cluster with surrounding star fields. In a 2,032 mm Schmidt-Cassegrain with a 2 in diagonal, it gives 51x and a field of about 1.3 degrees.

The exit pupil is large: about 6.8 mm in an f/5.9 telescope. That is near the maximum pupil of a young eye, so the view is as bright as the telescope can make it. In slower telescopes, the exit pupil is smaller and the sky looks darker.

Stars stay sharp across most of the field at f/6 and slower. In faster Newtonians, the outer field shows coma from the telescope, which a coma corrector removes. The lenses are fully multi-coated.

The 24 mm eye relief is long enough for observers with glasses to see the whole field. A twist-up eyecup sets the eye position for observers without glasses.

At 700 g, the Strider 40 mm is a substantial eyepiece. It suits large Dobsonians and Schmidt-Cassegrains with 2 in diagonals, where it serves as the finding and survey eyepiece.

About this configuration

All configurations of the Halden Strider 40 mm wide-field eyepiece share the same optical design; the options change the eyecup, the case, and the finish. 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. With a twist-up eyecup, you can raise or lower the cup in steps to match your eye relief needs.

Black anodizing is the standard finish of the Strider line and matches most focusers. This is the 2025 edition, which added a safety groove to the barrel and a firmer eyecup detent. 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 twist-up eyecup
• Top and bottom dust caps
• Foam-lined storage case

Compatibility notes

• Needs a 2 in focuser or 2 in star diagonal.
• The barrel accepts standard 2 in filters (M48 x 0.75 thread).
• In telescopes faster than f/5, the exit pupil exceeds 7 mm and part of the light is lost.