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Extension tubes

CHICIRIS 1.25 in to 2 in adapter

An adapter taking a 1.25 in eyepiece into a 2 in focuser, held by a brass compression ring rather than a bare thumbscrew.

CHICIRIS 1.25 inch to 2 inch telescope eyepiece adapter

CHICIRIS 1.25 in to 2 in adapter

An adapter taking a 1.25 in eyepiece into a 2 in focuser, held by a brass compression ring rather than a bare thumbscrew.

Length
The listing gives none
Barrel and thread fittings
Holds a 1.25 in (31.7 mm) eyepiece in a 2 in (50.8 mm) focuser · Not mentioned
Internal blackening
Not published by the maker.
Clamping method
Brass compression ring, per the maker
Rigidity
Not published by the maker.
Material
Anodised aluminium
Amazon reference
B083587TGB (same reference on 5 Amazon marketplaces)
EAN
0738588852611
  • A brass compression ring protects the eyepiece barrel and keeps it centred
  • The conversion almost every 2 in focuser owner needs at some point
  • No length figure, and an adapter changes where the focal plane falls

Best for: A 2 in focuser used with a collection of 1.25 in eyepieces

≈ €26
Check price on Amazon

Specifications

Length
The listing gives none
Barrel and thread fittings
Holds a 1.25 in (31.7 mm) eyepiece in a 2 in (50.8 mm) focuser · Not mentioned
Internal blackening
Not published by the maker.
Clamping method
Brass compression ring, per the maker
Rigidity
Not published by the maker.
Material
Anodised aluminium
Amazon reference
B083587TGB (same reference on 5 Amazon marketplaces)
EAN
0738588852611

The adapter every 2 in focuser needs

Most collections start in 1.25 in and most larger telescopes have a 2 in focuser. This part bridges them, and a telescope that came with a 2 in focuser and no adapter is a telescope that cannot use the eyepieces its owner already has.

The compression ring

Brass, and the reason to choose this over the cheapest alternative. A single thumbscrew dents the eyepiece barrel and tilts it; a compression ring grips a continuous band and keeps it square to the axis. On a wide-field eyepiece at high magnification, that squareness is visible.

The number that never appears

Length. Any adapter occupies optical path, and where the focal plane falls changes accordingly. For visual use the focuser absorbs it; for imaging it has to be counted.

What it cannot do

Widen anything. A 1.25 in eyepiece in a 2 in focuser still sees a 1.25 in field stop. The adapter solves a mechanical problem and leaves the optical one where it was.

Availability

German, French, Italian and Spanish Amazon stores ran from 26 € to 30 € on the day of the survey.

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

American Amazon store gave no result whatever, so the buy button there opens a search rather than an empty page.

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 extension tubes

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    A 2 in extension sleeve of 50 mm optical path with a spring-ring clamp, a filter thread at the lower end and internal ribbing against reflections.

    Length
    50 mm, as the maker publishes it
    Barrel and thread fittings
    2 in · 2 in, at the lower end
    Internal blackening
    Ribbed inside against reflections, black anodised outside
    Clamping method
    2 in spring-ring clamp, per the maker
    Rigidity
    Not published by the maker.
    Material
    Not published by the maker.
    Amazon reference
    B074FQH48F (same reference on 6 Amazon marketplaces)
    EAN
    4049467550723
    • Publishes the optical path added, which is the only figure that matters for an extension
    • A spring-ring clamp grips the barrel evenly instead of denting it with a screw
    • Fifty millimetres is a large step; finer adjustment needs a set of thin rings

    Best for: A telescope whose focal plane sits too far out for its eyepieces to reach

    ≈ £36 / €39
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  • Explore Scientific set of five M48 extension sleeves

    Explore Scientific M48 extension sleeve set (0510381)

    Five threaded extension sleeves of 30, 20, 15, 10 and 5 mm, all M48 × 0.75, for fine adjustment of back focus in an imaging train.

    Length
    Not published by the maker.
    Barrel and thread fittings
    M48 × 0.75 on every sleeve
    Internal blackening
    Not published by the maker.
    Clamping method
    Not published by the maker.
    Rigidity
    Not published by the maker.
    Material
    Not published by the maker.
    Amazon reference
    B085HYZT9Y (same reference on 5 Amazon marketplaces)
    EAN
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    • Five published lengths that combine to any multiple of 5 mm up to 80
    • Threaded rather than push-fit, so nothing can tilt or slip in a long exposure
    • M48 only: a T2 train needs adapters at each end

    Best for: Dialling in the exact sensor spacing a reducer or flattener demands

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  • Topiky 60 mm 2 inch telescope extension tube

    Topiky 2 in extension tube, 60 mm

    A 60 mm 2 in extension tube in anodised aluminium with two brass-tipped locking screws to stop an inserted barrel slipping.

    Length
    60 mm, from the title · Not distinguished from the physical length in the listing
    Barrel and thread fittings
    2 in
    Internal blackening
    Black anodised, described as avoiding unwanted reflections
    Clamping method
    Two thumbscrews with brass locking tips, per the maker
    Rigidity
    Not published by the maker.
    Material
    Aluminium alloy
    Amazon reference
    B07VWQRT4P (same reference on 5 Amazon marketplaces)
    EAN
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    • Brass tips under the thumbscrews prevent an inserted barrel being marked
    • Two screws rather than one, which holds a heavy eyepiece more securely
    • The listing does not say whether 60 mm is the physical length or the optical path added

    Best for: A 2 in focuser that needs a substantial, inexpensive extension

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The rest of this rack

  • Briny River M42 to M48 anodised aluminium step-up ring

    Briny River M42 to M48 step-up ring (390-EG)

    A step-up ring converting the T-2 thread to M48, so that 2 in filters and M48 accessories can be fitted to T-2 components.

    Slot count and filter size
    M42 × 0.75 male — the T-2 thread · M48 × 0.75 female — the 2 in filter thread
    Optical path length
    The listing gives none
    Manual or motorised operation
    A thread adapter — no optics, and not a filter wheel
    Light sealing
    Aluminium alloy, anodised
    Power
    Not published by the maker.
    Software support
    Not published by the maker.
    Amazon reference
    DE B0FM49SGJH · US B0FM48JF46 · GB B0FM48JF46 · FR B0FM48JF46 · IT B0FM48JF46 · ES B0FM48JF46
    EAN
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    • Both threads are named precisely with pitch, which is what an adapter listing must do
    • Anodised aluminium resists the corrosion that ruins a thread left damp
    • No length figure, and every adapter consumes back focus

    Best for: Putting an M48 filter or accessory onto a T-2 threaded component

    ≈ €9
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  • ECSiNG M48 to M42 double-male adapter ring

    ECSiNG M48 male to M42 male adapter

    A male-to-male ring joining M48 × 0.75 to M42 × 0.75 with the shortest possible mechanical length, blackened inside against reflections.

    Slot count and filter size
    M48 × 0.75 and M42 × 0.75, both male
    Optical path length
    Described as the minimum mechanically possible; no figure is given
    Manual or motorised operation
    A thread adapter — no optics, and not a filter wheel
    Light sealing
    Aluminium, anodised black with a matt internal wall
    Power
    Not published by the maker.
    Software support
    Not published by the maker.
    Amazon reference
    B0C7BYJ588 (same reference on 5 Amazon marketplaces)
    EAN
    4895243557307
    • The matt internal finish addresses internal reflections, which few adapter listings mention
    • Both threads are named with their pitch
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    Best for: Joining two female-threaded components of different sizes in an imaging train

    ≈ €10
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  • NVZPG M48 to M28.5 filter adapter ring

    NVZPG AP M48 to M28.5 filter adapter

    A threaded ring that holds a 1.25 in filter in a 2 in filter drawer, converting M48 to M28.5.

    Slot count and filter size
    M48 to M28.5 — the 2 in filter thread to the 1.25 in filter thread
    Optical path length
    Not published by the maker.
    Manual or motorised operation
    A filter adapter ring — not a wheel and not a drawer
    Light sealing
    Not published by the maker.
    Power
    Not published by the maker.
    Software support
    Not published by the maker.
    Amazon reference
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    EAN
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    • Solves a real and common problem for a few euros
    • Both threads are named precisely rather than given as inch sizes alone
    • A 1.25 in filter in a 2 in path can vignette a large sensor

    Best for: An imaging train with a 2 in drawer and a collection of 1.25 in filters

    ≈ £35 / €42
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