Magnification is a division, not a number on a box · review
A 4 mm (0.16 in) four-element Plössl whose own listing claims long eye relief — on the shortest focal length this shelf carries.
The first bullet: give wider view field along with extra sharpness and long eye relief.
The published page for the Orbinar 10 mm (0.39 in) on this shelf: a Plössl’s eye relief is roughly proportional to its focal length, so a 10 mm (0.39 in) is tight.
This is four. It is the shortest focal length on either half of this shelf.
Neither text publishes a figure, so neither can be checked against the other. Both are printed here.
The same maker’s 8 mm (0.31 in) is already published on this shelf, and its page records that its listing promises the widest field of view — for fifty degrees.
This one says generous fifty, and wider view field, in one sentence.
Fifty is the classic Plössl number. The wide-field designs on this shelf publish 60, 62 and 66.
One maker, one unchanging figure, and the adjective moving.
Up for the naked eye, down for spectacles — and stated to stop glasses being scratched during long sessions.
That second reason is the practical one, and it is the sentence a 4 mm (0.16 in) eyepiece needs, because the eye has to come very close.
It does not substitute for a relief figure. It is what the maker offers instead of one.
The strongest of the four labels, claimed without qualification.
Coated is one layer somewhere; fully coated is one layer on every air-to-glass surface; multi-coated is several layers somewhere; fully multi-coated is several on every surface.
A four-element Plössl is two cemented pairs — four air-to-glass surfaces — so the claim is worth less here than on the six-element eyepiece published beside it, and it is still the right claim to make.
The least expensive American eyepiece on this shelf, in a machined aluminum body with rigid caps.
On the European half the range runs from about seventeen to about ninety-three, and the page at the top of it does not publish its eye relief either.
American Amazon store sat at about $16 on the day of the survey.
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 October 7, 2026. The live price is at the top of the page.
Same aisle, closest price — what the same spend else shows.
| Focal length | 4 mm (0.16 in) — the shortest on this shelf |
|---|---|
| Apparent field | 50 degrees, stated generous, and stated in the same bullet to give a wider view field |
| Eye relief | No figure published. The first bullet states long eye relief · A fold-down rubber eyeguard, stated to cushion the eye and to protect spectacles from scratching |
| Barrel size | 1.25 in, with a female filter thread for standard 1.25 in filters, stated to fit any 1.25 in focuser on a refractor, reflector or catadioptric |
| Optical design | Plössl, four elements |
| Coatings | Fully multi-coated, stated to maximize transmission, contrast and image clarity |
| Weight | Not published by the maker. · The body is stated machined from premium aluminum alloy, and stated lightweight |
| Supplied accessories | Sturdy plastic dust caps, stated to protect the lens from dust, moisture and scratches |
| Amazon reference | B0140UANS4 |
| EAN | 6970019290461 |
The listing says it does and this shelf’s own published pages say the opposite. The first bullet reads: give wider view field along with extra sharpness and long eye relief. The published page for the Orbinar 10 mm (0.39 in) on this shelf states that a Plössl’s eye relief is roughly proportional to its focal length, so a 10 mm (0.39 in) is tight — and this is 4 mm (0.16 in). Neither text carries a figure, so neither can be checked. This page prints both and leaves the arithmetic to the reader.
Fifty degrees is the classic Plössl figure. The published page for this same maker’s 8 mm (0.31 in) on this shelf already notes that its listing promises the widest field of view for the same fifty degrees — and wide-field designs on this shelf reach 60, 62 and 66. So the phrase recurs across one maker’s range at one unchanging number. The field is real; the adjective is the maker’s.
Divide the telescope’s focal length by four and compare with about twice the aperture in millimeters. On a 900 mm (35.4 in) f/8 reflector it gives 225x, which a 114 mm (4.49 in) objective cannot support. On a 1500 mm (59.1 in) Maksutov it gives 375x, which only the steadiest nights allow. The published SVBONY 4 mm (0.16 in) aspheric on this shelf runs the same arithmetic to the same conclusion, and this listing — like that one — prints no magnification, correctly, because an eyepiece has none of its own.
This model is listed on Amazon.com, at ≈ $16 at the last reading. Listed is not the same as in stock: availability changes daily, and the buy box shows the live price.
Details checked on October 7, 2026.
High-power lunar and planetary work on a long-focal-length telescope, by somebody who does not wear spectacles at the eyepiece
Specifications: the manufacturer sheet for telescopes and observing optics and the matching Amazon product page. Prices and availability: Keepa. Every figure on this page names its source.
8 mm (0.31 in) focal length · apparent field stated two ways · four elements
A four-element fully multi-coated Plössl of 8 mm (0.31 in) 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 (0.39 in) focal length · four elements in two groups · 65 g (2.3 oz)
A 10 mm (0.39 in) Plössl with four elements in two groups, fully multi-coated, in a metal housing with a filter thread, published at 65 g (2.3 oz).
Best for: A dependable mid-power eyepiece for a case that is being built properly
6 mm (0.24 in) focal length · 50° apparent field · four elements · blackened lens edges · anodized aluminum
A 6 mm (0.24 in) Plössl with blackened lens edges and an anodized aluminum body, at 50 degrees — and a two-year warranty published.
Best for: Planetary detail on a medium-focal-length telescope, from a maker that publishes a warranty
≈ $32
