They pass the lines the gas emits and block the rest · review
The 2 in oxygen filter: the same two lines as its 1.25 in sibling, plus a named coating process and a halo claim the smaller one does not make.
Both Celestron oxygen filters on this shelf isolate 496 and 501 nanometers. Both name the Veil, the Ring, the Dumbbell, the Crescent and Orion. Both carry the same two-year warranty.
This one adds an ultra-hard, vacuum-deposited coating, and states that it eliminates un-natural colored halos round bright stars.
The 1.25 in names no coating and makes no halo claim.
Nothing on either page explains the difference. Both sets of claims are printed here, and this page does not assume the smaller filter is merely less well described.
The only coating process named on this shelf.
Every other listing here gives a label — coated, multi-coated, fully multi-coated, double-sided multi-layer — which describes the result. This one describes the method: the layers laid down in a vacuum chamber rather than dipped.
Harder, and more uniform. Which is the mechanism behind the next claim.
Rings of color round bright stars, caused by light reflecting between the two faces of a filter and returning through it at a slight angle.
It is the characteristic fault of a narrowband filter whose coatings are not well matched, and it shows up exactly where it is most visible: round the brightest star in the field.
A uniform coating is the cure. No figure, no test, and no before-and-after is published — only the claim.
The only two-inch filter on this shelf.
Several of the seven listings here assume a 1.25 in focuser. A 2 in filter screws into the back of a 2 in eyepiece or into a 2 in diagonal, and cannot serve a 1.25 in eyepiece without an adapter; a 1.25 in filter vignettes a 2 in eyepiece badly.
So the choice is not which is better. It is which barrel the rest of the equipment uses — and for a 2 in focuser, this shelf offers exactly one answer.
The lines are five nanometers apart, so the window is at least that wide.
How much wider is unpublished here, as it is on every other filter on this shelf.
Four listings now give wavelengths. None gives a width, and none gives a transmission percentage.
American Amazon store sat at about $95 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.
| Bandpass and type | Oxygen III narrowband, isolating the two doubly-ionized oxygen lines at 496 and 501 nm, per the maker, while blocking the rest of the spectrum · The bandwidth around them is not published · The Veil, the Ring, the Dumbbell, the Crescent and Orion, named by the maker |
|---|---|
| Line transmission | Not published by the maker. |
| Blocking outside the band | The rest of the overall spectrum of light, per the maker · Stated to give extreme contrast between the black sky background and the faint OIII photons · No optical density figure is published |
| Thread size | 2 in — the only 2 in filter on this shelf |
| Glass flatness | Not published by the maker. |
| Coatings | An ultra-hard, vacuum-deposited coating, as the maker words it — the only coating process named on this shelf · The number of layers and the faces treated are not given · Stated to eliminate un-natural colored halos surrounding bright stars — a claim the maker’s 1.25 in version does not make |
| Amazon reference | B0007UQNWM |
| EAN | 0050234936248 |
Nothing on either page explains it. Both isolate 496 and 501 nm, both name the same five objects, both come from the same maker with the same warranty. This one adds an ultra-hard vacuum-deposited coating and the elimination of colored halos round bright stars; the smaller one names no coating and makes no halo claim. The two listings are the same product in two diameters with two different sets of arguments, and this page prints both sets rather than assuming the smaller one is simply less well described.
Rings of color round bright stars, produced when light reflects between the faces of a filter and comes back through at a slight angle. They are the characteristic fault of a narrowband filter with poorly matched coatings, and they are worst exactly where they are most visible — round the brightest stars in the field. A coating applied by vacuum deposition is harder and more uniform than a dipped one, which is the mechanism behind the claim. No figure accompanies it.
Only if the focuser and the eyepiece are 2 in. A 2 in filter screws into the back of a 2 in eyepiece or into a 2 in diagonal; it cannot be used with a 1.25 in eyepiece without an adapter, and a 1.25 in filter vignettes a 2 in eyepiece badly. The question is not which filter is better but which barrel the rest of the equipment uses. This is the only 2 in filter on either half of this shelf, which is itself a finding: several of the seven listings here assume a 1.25 in focuser.
This model is listed on Amazon.com, at ≈ $95 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.
A 2 in focuser and a wide-field eyepiece, on planetary nebulae and supernova remnants
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.
UHC · M28.5 × 0.6 thread · aluminum alloy frame · waterproof coating · no passband published
A UHC filter whose published features include a first-person account of seeing the Orion nebula — and no wavelength anywhere.
Best for: A first nebula filter for a light-polluted sky, bought on price with the specification taken on trust
≈ $23
H-alpha narrowband · 1.25 in · hardened multi-coatings · no bandwidth published
A narrowband hydrogen-alpha filter whose bandwidth — the one figure that defines a narrowband filter — is never published.
Best for: Imaging hydrogen regions, by somebody who will ask the seller for the bandwidth before buying
≈ $70
UHC · 1.25 in standard thread · optical glass in an aluminum frame · anti-reflection coatings · no passband published
A UHC filter that explains correctly what the category does, names the nebulae it suits, and publishes no wavelength at all.
Best for: An observer in a suburban sky who wants the effect explained before buying, and will take the glass on trust
≈ $32
