One barrel across a range, with a field that narrows · review
Publishes the apparent field at both ends — 30 degrees at 21 mm (0.83 in), 47 at 7 — which is the central compromise of every zoom.
One of two pairs of field figures on this shelf.
A zoom is designed around its short focal length, and the field stop cannot grow as the focal length does. So the long end is the weak end: thirty degrees at 21 mm (0.83 in), against roughly fifty for a fixed 20 mm (0.79 in) Plössl.
At the short end it recovers: forty-seven degrees at 7 mm (0.28 in), which is near what a fixed eyepiece of that focal length gives.
That is the central compromise of every zoom ever made, and two listings on this shelf print it as two numbers instead of leaving it to be discovered.
The widest eye relief range published here, and the listing names what it is for: changing magnification without changing eyepiece.
Swapping a 20 mm (0.79 in) for a 7 mm (0.28 in) in the dark means unscrewing, fumbling, refocusing, and usually losing the object. A zoom removes that, and a zoom with thirty-three millimeters of relief at its long end lets spectacles stay on throughout.
A fixed 7 mm (0.28 in) Plössl has about five millimeters. Nobody wears glasses behind one.
One sentence, and the only one of its kind on this shelf.
Seven millimeters is not a magnification. On a 700 mm (27.6 in) refractor it is 100x; on a 1500 mm (59.1 in) Maksutov, 214x. The first is comfortable on a 70 mm (2.76 in) aperture, the second needs a steady night on a larger one.
The eyepiece shelf in this catalog runs the same arithmetic on a fixed 4 mm (0.16 in), and reaches the same place: the figure belongs to the reader’s own tube.
Fully multi-coated, claimed as an abbreviation and never expanded.
The ladder behind it: 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 zoom has more air-to-glass surfaces than a fixed eyepiece — that is the price of the mechanism — so the coating claim matters more here than almost anywhere, and the surfaces are not named.
Clicked or stepless, unknown.
The Alstar beside it on this shelf states stepless; the published Celestron on the European half has defined stops. This one publishes a rubber traction ring and leaves the mechanism out.
It is the difference between returning to a known magnification and sweeping for a comfortable one, and this page cannot say which it does.
American Amazon store sat at about $52 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 range | 21 mm (0.83 in) down to 7 mm (0.28 in), stated to give a variety of magnifications · Actual magnification stated to depend on the telescope’s focal length |
|---|---|
| Apparent field at both ends | 30 degrees at 21 mm (0.83 in) and 47 degrees at 7 mm (0.28 in) — one of two field pairs published on this shelf, with the Celestron 8–24 mm |
| Eye relief | 16 to 33 mm (0.63 to 1.30 in), stated exceptionally long, and stated to allow the magnification to be changed without changing eyepiece |
| Parfocality | Not published by the maker. |
| Action | Not published as stepped or stepless · A rubber traction ring is stated to ensure a good grip |
| Stops | Not published by the maker. |
| Barrel size | 1.25 in, threaded for standard filters |
| Coatings | FMC — fully multi-coated, per the title |
| Body | A rubber traction ring for grip |
| Amazon reference | B0719FL3K4 |
| EAN | 6970019298863 |
It is narrow, and it is the honest number. A fixed 20 mm (0.79 in) Plössl gives about fifty degrees; this zoom gives thirty at its 21 mm (0.83 in) end and forty-seven at its 7 mm (0.28 in) end. The reason is that a zoom is designed around its short focal length, and the field stop cannot grow as the focal length does. So the long end of any zoom is its weak end, and the published European zooms on this shelf give 40 to 60 degrees on one listing and nothing on the other. Publishing both numbers is what lets a reader see the compromise instead of discovering it.
Because the listing names the real benefit: the magnification can be changed without changing eyepiece. That sounds obvious and it is the whole point — swapping a 20 mm (0.79 in) for a 7 mm (0.28 in) in the dark means unscrewing, fumbling, refocusing and often losing the object. Sixteen to thirty-three millimeters also means spectacles stay on at every setting, where a fixed 7 mm (0.28 in) would have about five millimeters and be unusable with them. It is the strongest argument any zoom on this shelf makes.
More magnification than most small apertures can use. On a 700 mm (27.6 in) refractor, 7 mm (0.28 in) gives 100x, which a 70 mm (2.76 in) objective carries; on a 1500 mm (59.1 in) Maksutov it gives 214x, which needs a steady night. The listing says plainly that actual magnification depends on the telescope’s focal length, which is a sentence the rest of this shelf leaves out. The eyepiece shelf in this catalog runs the same arithmetic on a fixed 4 mm (0.16 in) and reaches the same conclusion.
This model is listed on Amazon.com, at ≈ $52 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.
One eyepiece instead of four, by somebody who wants to know what the long end costs in field
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.
8–24 mm (0.31 to 0.94 in) variable · 15–18 mm (0.59 to 0.71 in) eye relief · stepless twist action · foldable eyecup · 1.25 in
Eight to twenty-four millimeters with eye relief published at both ends — 15 to 18 mm (0.59 to 0.71 in), which is what makes a zoom usable with spectacles.
Best for: A spectacle wearer who wants one eyepiece instead of four, with eye relief guaranteed at every setting
≈ $78
8–24 mm (0.31 to 0.94 in) variable · 1.25 in and 2 in · M43 camera thread
An 8–24 mm (0.31 to 0.94 in) zoom that fits both 1.25 in and 2 in focusers and carries an M43 camera thread, supplied with an extensive accessory set.
Best for: An owner of both 1.25 in and 2 in focusers who also photographs through the eyepiece
≈ $396
8–24 mm (0.31 to 0.94 in) variable · 40°–60° apparent field · 1.25 in
Celestron 93230 8–24 mm zoom eyepiece, 1.25 in: a 40° to 60° apparent field published across the range, multi-coated, fold-down eyecup. No US seller now.
Best for: Observers who want to stop swapping eyepieces in the cold
