Magnification is a division, not a number on a box · review
A 4 mm aspheric eyepiece with a 62-degree apparent field, fully coated, in a 51 mm aluminium barrel with an M28.5 × 0.6 filter thread.
The bottom line A wide-field short eyepiece with unusually precise fittings data, and a coating label one step below its neighbours.
A wide apparent field on a short eyepiece is worth having: at high magnification the sky drifts quickly, and a wide field buys time between nudges on an undriven mount.
M28.5 × 0.6 for the filter thread, 51 mm of length, about 42 g of mass. The first removes guesswork about filters; the second matters for eyepiece projection with a T-ring, which the maker names as an intended use; the third keeps the balance of a small telescope undisturbed.
“Fully coated” means every air-to-glass surface carries one layer. The Plössls beside it on this shelf claim “fully multi-coated”, which is several layers per surface. On an aspheric design with fewer surfaces the gap is smaller than it would otherwise be, and it is still a gap.
Four millimetres is a very short eyepiece. Work out the magnification on your own telescope and the exit pupil — the eyepiece focal length divided by the focal ratio — before deciding. At f/5 this gives a 0.8 mm exit pupil, which is demanding on the eye.
Italian Amazon store sat at about 20 € on the day of the survey.
British Amazon store lists it in local currency, which the euro range above sets aside.
German, French and Spanish Amazon catalogues hold a record for it that nobody is selling.
American Amazon store gave no result whatever, so the buy button there opens a search rather than an empty page.
Figures as Keepa reported them on the day this page was last updated. Stock and pricing shift without warning.
Prices quoted in this text were read on 17 September 2026. The live price is at the top of the page.
| Focal length | 4 mm |
|---|---|
| Apparent field | 62 degrees, as the maker states it |
| Eye relief | Not published by the maker. |
| Barrel size | 1.25 in, with an M28.5 × 0.6 filter thread named by the maker |
| Optical design | Aspheric |
| Coatings | Fully coated, as the maker words it |
| Weight | 1.48 oz / 0.09 lb — about 42 g |
| Supplied accessories | Two dust caps |
| Amazon reference | B0749PC72L (same reference on 5 Amazon marketplaces) |
| EAN | 0609378744389 |
Divide your focal length by 4, then compare with roughly twice your aperture in millimetres. On a 900 mm f/8 telescope it gives 225x, which a 114 mm cannot support. On a 1500 mm Maksutov it gives 375x, which only the steadiest nights allow.
Because it removes the ambiguity. “1.25 inch” describes the barrel; M28.5 × 0.6 describes the thread cut inside it, and that is what a filter actually screws into.
8 mm focal length · apparent field stated two ways · four elements
A four-element fully multi-coated Plössl of 8 mm focal length in a metal 1.25 in barrel, with a fold-down rubber eyecup and a filter thread.
Best for: A step up from a supplied short eyepiece, on a case-based collection
≈ $17
10 mm focal length · four elements in two groups · 65 g
A 10 mm Plössl with four elements in two groups, fully multi-coated, in a metal housing with a filter thread, published at 65 g.
Best for: A dependable mid-power eyepiece for a case that is being built properly
≈ €25
25 mm focal length · 50° apparent field · four elements
A 25 mm Plössl with a 50-degree apparent field, coated optics, a metal body, rubber eyecups and a filter thread.
Best for: The finding eyepiece — the one that stays in the focuser most of the evening
≈ £32 / €34
