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Light pollution filters

Omegon Pro CLS 2 in

A 2 in broadband CLS filter that the maker states suits telescopes from 70 mm upwards and darkens the object only slightly.

Omegon Pro CLS 2 inch light pollution filter

Omegon Pro CLS 2 in

A 2 in broadband CLS filter that the maker states suits telescopes from 70 mm upwards and darkens the object only slightly.

Blocked wavelengths and published curve
The listing gives none as wavelengths
LED and sodium behaviour
Not published by the maker.
Visual or photographic design
CLS broadband filter, 2 in thread
Colour cast
Not published by the maker.
Thread size
Not published by the maker.
Focal ratio limits
From 70 mm, as the maker states it
Amazon reference
B016O66DY0 (same reference on 6 Amazon marketplaces)
EAN
4049467472919
  • The maker states a minimum aperture, which almost no filter listing does
  • A 2 in thread suits wide-field eyepieces and 2 in focal adapters
  • No wavelengths and no transmission percentage appear anywhere

Best for: A 2 in eyepiece or focal adapter on a telescope of 70 mm or more, under a town sky

≈ £83 / €93
Check price on Amazon

Specifications

Blocked wavelengths and published curve
The listing gives none as wavelengths
LED and sodium behaviour
Not published by the maker.
Visual or photographic design
CLS broadband filter, 2 in thread
Colour cast
Not published by the maker.
Thread size
Not published by the maker.
Focal ratio limits
From 70 mm, as the maker states it
Amazon reference
B016O66DY0 (same reference on 6 Amazon marketplaces)
EAN
4049467472919

One useful figure, and it is not optical

Seventy millimetres of aperture as a stated minimum. That is guidance about when the filter is worth using at all, and it comes from the trade every filter makes: light removed against contrast gained. Few listings on this shelf offer it.

The blanks in the listing

The passband and the transmission. Beside it on this site sits a CLS filter that names five emission lines at 90 per cent and three lamp lines at 0.1 per cent. Against that, a description written as narrative cannot be placed.

The 2 in fitting

Larger than the common 1.25 in, and matched to wide-field eyepieces and 2 in focal adapters. On a short telescope that combination gives the widest possible true field with the filter in place, which is where a broadband filter shows best.

The expectation to carry into the field

Nothing gets brighter. The sky behind the object darkens, and the object stands out against it. On an emission nebula from a town that is a real gain; on a galaxy it is not.

Availability

German, French, Italian and Spanish Amazon stores ran from 93 € to 96 € on the day of the survey.

British Amazon store lists it in local currency, which the euro range above sets aside.

American Amazon catalogue holds a record for it that nobody is selling.

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.

What this fits

More light pollution filters

  • SVBONY 1.25 inch CLS light pollution filter

    SVBONY CLS 1.25 in (FUSF9155A)

    A CLS broadband filter publishing 90 per cent transmission at the hydrogen, oxygen and sulphur lines and 0.1 per cent at the sodium and mercury lines of artificial lighting.

    Blocked wavelengths and published curve
    90 % at Hα 656 nm, O-III 496 and 500 nm, S-II 672 nm and Hβ 486 nm, as the maker publishes it
    LED and sodium behaviour
    0.1 %, named at Na 589 and 578 nm and Hg 435 nm
    Visual or photographic design
    CLS broadband filter, threaded for 1.25 in eyepieces and camera noses
    Colour cast
    Planetary rotation coating system, for uniformity — the maker’s own description
    Thread size
    Not published by the maker.
    Focal ratio limits
    Not published by the maker.
    Amazon reference
    B079BWD595 (same reference on 6 Amazon marketplaces)
    EAN
    0609378745577
    • The only filter on this shelf to publish both in-band and off-band transmission with named wavelengths
    • The blocked lines are named by element, which is what allows the claim to be checked against physics
    • A broadband filter helps less than a narrowband one under heavy light pollution

    Best for: Imaging or observing emission nebulae from a town, with a colour camera or by eye

    ≈ $32 / €46
    Check price on Amazon
  • K&F Concept Nano-X 67 mm natural night filter

    K&F CONCEPT Nano-X Natural Night 67 mm

    A 67 mm photographic light-pollution filter blocking the 580 to 610 nm region of common artificial lighting, with a 28-layer nano coating on both faces.

    Blocked wavelengths and published curve
    Approximately 580 to 610 nm, as the maker publishes it
    LED and sodium behaviour
    Not published by the maker.
    Visual or photographic design
    Screw-in filter for a camera lens — not a telescope filter
    Colour cast
    28 layers, double-sided nano coating per the maker · Japanese optical glass, double-side polished, per the maker
    Thread size
    67 mm
    Focal ratio limits
    Not published by the maker.
    Amazon reference
    B07PG785HC (same reference on 6 Amazon marketplaces)
    EAN
    6936069223248
    • The blocked region is published as a wavelength range rather than described
    • Double-sided coating reduces the ghosting that plagues bright-light nightscapes
    • It is a camera filter: it will not thread into an eyepiece or a telescope nose

    Best for: Wide-field tracked photography with a camera lens under sodium-lit skies

    ≈ £42 / €55
    Check price on Amazon

The rest of this rack

  • Vixen 1.25 inch moon filter

    Vixen Moon filter 1.25 in (37222-5)

    A plane-parallel Moon filter that screws into 1.25 in eyepieces, sold on the quality of its substrate rather than on a stated transmission.

    Transmission percentage
    The listing gives none anywhere in the listing
    Neutral or tinted dimming
    Not published by the maker.
    Fixed or variable design
    Moon filter, threaded for 1.25 in eyepieces
    Thread size
    Not published by the maker.
    Glass flatness
    High-quality plane-parallel glass, as the maker states it
    Cell depth
    Not published by the maker.
    Amazon reference
    B0018HILMI (same reference on 6 Amazon marketplaces)
    EAN
    4955295372225
    • Plane-parallel glass is the property that keeps the image sharp at high magnification
    • A 1.25 in thread fits the eyepiece size almost everyone owns
    • No transmission percentage, so it cannot be compared with the filters beside it

    Best for: A 1.25 in eyepiece case where substrate quality matters more than a published figure

    ≈ $54 / £42 / €45
    Check price on Amazon
  • Diealles Shine black telescoping folding stool

    Diealles Shine Telescoping folding stool

    A polypropylene telescoping stool with a carry strap, described in five bullets that contain no measurement at all.

    Seat height range
    The listing gives none
    Adjustment method
    Not published by the maker.
    Steps
    The listing gives none
    Load rating
    The listing gives none — described as a large capacity
    Folded size
    The listing gives none
    Weight
    The listing gives none
    Foot design
    Not published by the maker.
    Seat material
    Polypropylene, described as an upgraded version
    Supplied accessories
    Supplied straps for hand or shoulder
    Amazon reference
    B0BWF25TX6 (same reference on 5 Amazon marketplaces)
    EAN
    0788135722737
    • The same telescoping principle as its better-documented rivals
    • Carry straps are supplied rather than sold separately
    • Not one measurement appears anywhere in the listing

    Best for: Nobody who has not seen one in person or measured what they need

    ≈ €20
    Check price on Amazon
  • Have A Seat telescoping stool in black with cushion

    Have A Seat HAS-001 telescoping stool

    An eleven-step telescoping stool reaching 45 cm with a 25 cm seat, a cushion and a bag, listed at 1.5 kg in its title and 1160 g in its bullets.

    Seat height range
    Eleven, reaching 45 cm
    Adjustment method
    A spring mechanism that engages each step, per the maker
    Steps
    Not published by the maker.
    Load rating
    Not given as a figure; described as carrying an average adult
    Folded size
    25 cm
    Weight
    The title says 1.5 kg; the fourth bullet says 1160 g. Both are reproduced here
    Foot design
    Not published by the maker.
    Seat material
    Described by the maker as patented
    Supplied accessories
    Seat cushion, bag and carry handle
    Amazon reference
    B09QMNJ4TW (same reference on 5 Amazon marketplaces)
    EAN
    4170000029076
    • Eleven steps to 45 cm covers the range a telescope actually needs
    • A spring mechanism that clicks into each step is quicker than a twist lock
    • The listing gives two different weights for the same stool

    Best for: An observer who wants a quick spring lock rather than a twist mechanism

    ≈ €35
    Check price on Amazon

All light pollution filters