Brightwell Orbit 5 mm planetary eyepiece

Specifications

Description

The Orbit 5 mm is a six-element planetary eyepiece with a 58-degree apparent field and a 1.25 in barrel. It is designed to give high magnification with comfortable eye relief, which simple short focal length designs cannot do.

In a 1,200 mm Dobsonian, the Orbit 5 mm gives 240x. In a 700 mm refractor it gives 140x, and in a 1,500 mm Maksutov it gives 300x. Those magnifications suit the planets, the Moon, close double stars, and small planetary nebulae on nights when the air is steady.

The design places a negative lens group at the bottom of the barrel, which lengthens the eye relief to 16 mm. That lets you view with glasses and keeps your eye at a relaxed distance during long planetary sessions, when you wait for moments of steady air to reveal fine detail.

The lenses are fully multi-coated, and the internal surfaces are blackened to keep contrast high. A twist-up eyecup sets the eye position, and the 58-degree field gives a bit more time before an object drifts out of view in a telescope that does not track.

Magnification is limited by the atmosphere as much as by the telescope. On many nights, the air allows only 150x to 200x, so the Orbit 5 mm is a tool for the better nights. In a small telescope, it often runs close to the useful limit of the aperture, which is about twice the aperture in millimeters.

Pair the Orbit 5 mm with a medium-power eyepiece in the 10 mm to 15 mm range, so you can step down when seeing is poor.

About this configuration

The Brightwell Orbit 5 mm planetary eyepiece is offered in several configurations, and the notes below describe what this particular one adds. 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. 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 2025 edition, which added a safety groove to the barrel and a firmer eyecup detent. 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 twist-up eyecup
• Top and bottom dust caps
• Plastic storage case

Compatibility notes

• Fits any 1.25 in focuser or diagonal.
• The barrel accepts standard 1.25 in filters (M28.5 x 0.6 thread).
• Gives 240x in a 1,200 mm telescope; check that this is within the useful limit of your aperture.