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Bahtinov masks

MEOPTEX Bahtinov mask 175–220 mm

A laser-cut reinforced acrylic Bahtinov mask that clamps to tubes of 175 to 220 mm outside diameter with three silicone-sleeved metal posts.

MEOPTEX Bahtinov focusing mask on a telescope tube

MEOPTEX Bahtinov mask 175–220 mm

A laser-cut reinforced acrylic Bahtinov mask that clamps to tubes of 175 to 220 mm outside diameter with three silicone-sleeved metal posts.

Aperture
Not published by the maker.
Tube fit
175 to 220 mm, from the title · About 290–340 mm depending on model, as the maker words it
Slot geometry
Bahtinov focusing mask — it fits over the front of the tube
Focal ratio range
Reflectors, refractors, Dobsonians, Maksutov-Cassegrains and SCTs
Material
2 mm laser-cut reinforced acrylic, per the maker
Rigidity
The maker states it does not become brittle in the cold, unlike ordinary plastics
Mounting security
Three metal posts with non-scratching silicone sleeves
Obstruction clearance
Not published by the maker.
Amazon reference
B07KR2X2MX (same reference on 6 Amazon marketplaces)
EAN
6971680410547
  • Three-post mounting keeps the mask centred across a range of tube sizes
  • Silicone sleeves on the posts protect the tube finish
  • The title range and the stated adjustment range do not obviously agree

Best for: Focusing an imaging session precisely, on a tube whose outside diameter has been measured

≈ $21 / £18 / €26
Check price on Amazon

Specifications

Aperture
Not published by the maker.
Tube fit
175 to 220 mm, from the title · About 290–340 mm depending on model, as the maker words it
Slot geometry
Bahtinov focusing mask — it fits over the front of the tube
Focal ratio range
Reflectors, refractors, Dobsonians, Maksutov-Cassegrains and SCTs
Material
2 mm laser-cut reinforced acrylic, per the maker
Rigidity
The maker states it does not become brittle in the cold, unlike ordinary plastics
Mounting security
Three metal posts with non-scratching silicone sleeves
Obstruction clearance
Not published by the maker.
Amazon reference
B07KR2X2MX (same reference on 6 Amazon marketplaces)
EAN
6971680410547

Focusing as arithmetic rather than judgement

A Bahtinov mask makes a bright star throw three diffraction spikes. Two form an X and one crosses it; when the crossing spike sits exactly centred between the other two, the telescope is in focus. The eye judges symmetry far better than it judges sharpness, which is why the method works even in poor seeing.

The mounting is the engineering

Three metal posts with silicone sleeves, gripping the tube from three directions. That keeps the mask centred on the aperture across a range of diameters, where a simple friction ring would sit wherever it happened to land.

The material choice, explained

Two millimetres of reinforced acrylic, laser cut. The maker specifically contrasts it with ordinary plastics that go brittle in the cold — which is exactly when a mask is being handled, on a winter night with gloves on.

Measure before ordering

The outside diameter of the tube, at the front. Not the aperture. Those two are never equal, and the difference varies with construction.

Availability

German, French, Italian and Spanish Amazon stores ran from 26 € to 29 € on the day of the survey.

American and British Amazon stores list it in local currency, which the euro range above sets aside.

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

The rest of this rack

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    Method
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    Self-collimation ability
    Not published by the maker.
    Barrel fit
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    Play
    Not published by the maker.
    Brightness control
    Not published by the maker.
    Target visibility
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    Build
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    Suitable telescopes
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    Amazon reference
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    EAN
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    Check price on Amazon
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    Self-collimation ability
    Not published by the maker.
    Barrel fit
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    Play
    Not published by the maker.
    Brightness control
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    Target visibility
    Not published by the maker.
    Build
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    Suitable telescopes
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    Amazon reference
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    EAN
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    • A built-in battery removes the CR2032 problem on a cold night
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    Check price on Amazon
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    Method
    Laser collimator
    Self-collimation ability
    Metal · Not mentioned
    Barrel fit
    31.7 mm (1.25 in)
    Play
    Not published by the maker.
    Brightness control
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    Target visibility
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    Build
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All bahtinov masks