Quillon Marlin 21 mm Plössl eyepiece

Specifications

Description

The Marlin 21 mm is a four-element Plössl eyepiece with a 52-degree apparent field and a 1.25 in barrel. It sits in the middle of the focal range, between the low-power eyepieces that frame wide objects and the higher-power eyepieces that split close doubles and show planetary detail. Its 18 mm field stop sets the true field in each telescope, so the width of the view changes with focal length. It suits an observer building a set of three or four eyepieces.

A 21 mm eyepiece gives 33x in a 700 mm refractor, 57x in a 1,200 mm Dobsonian, and 97x in a 2,032 mm Schmidt-Cassegrain. In the 1,200 mm telescope, the true field is about 0.9 degrees, enough to frame a small open cluster or a compact group of galaxies. Moderate power gives a bright image with enough magnification to separate stars in open clusters and to show structure in brighter nebulae.

The Plössl design uses two cemented doublets facing each other. It gives sharp stars across most of the field in telescopes slower than about f/6, with some softening at the edge in faster Newtonians. The lenses are fully multi-coated, and the edges are blackened to reduce internal reflections that lower contrast under dark skies.

With 16 mm of eye relief, the Marlin 21 mm suits most observers, including many who wear glasses when the eyecup is folded down. At 80 g, it balances well on a diagonal and works in a binocular viewer. Pair it with a 10 mm eyepiece for higher power and a 32 mm eyepiece for wider fields.

About this configuration

The Quillon Marlin 21 mm Plössl 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. With a twist-up eyecup, you can raise or lower the cup in steps to match your eye relief needs.

The titanium gray finish has a hard anodized layer that resists wear from repeated insertion into focusers. 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 fold-down rubber eyecup
• Top and bottom dust caps
• Plastic storage 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 across most of the field at f/6 and slower.