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Extension tubes

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.

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
4007922064154
  • 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

≈ €55
Check price on Amazon

Specifications

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
4007922064154

Five numbers, and every sum between them

Thirty, twenty, fifteen, ten and five millimetres. Combined, they reach any multiple of five up to eighty. That is the toolkit for the one calculation in astrophotography that has no tolerance: the distance between a reducer and the sensor.

Why threads rather than barrels

A threaded joint holds a fixed distance and cannot tilt. A barrel clamped by a thumbscrew can sag under the weight of a camera and shift between exposures, and a shift of a fraction of a degree shows up as elongated stars in the corners.

The thin rings, explained

The maker names the smallest sleeves as fine-tuning rings and adds a second use: reducing how far a thread engages, so that two components seat where they are meant to rather than bottoming out. That is a real problem and it is rarely described in a listing.

The thread, and what it implies

M48 × 0.75 throughout. A T2 train will need an adapter at each end, and several suitable ones are on this shelf — each of which also consumes back focus and has to be counted.

Availability

German, French, Italian and Spanish Amazon stores ran from 55 € to 62 € 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

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    Length
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    Barrel and thread fittings
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    Internal blackening
    Black anodised, described as avoiding unwanted reflections
    Clamping method
    Two thumbscrews with brass locking tips, per the maker
    Rigidity
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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

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  • ZWWAAZHF spotting scope to DSLR camera adapter tube

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    Length
    Not published by the maker.
    Barrel and thread fittings
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    Internal blackening
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    Clamping method
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    Material
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    Amazon reference
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    EAN
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    • Names the exact scope models it is made for rather than claiming universality
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  • Bresser 37.5 mm M68 extension sleeve in aluminium

    Bresser Extension sleeve 37.5 mm for HEXAFOC (4940110)

    An aluminium extension sleeve of 37.5 mm with M68 × 0.75 male and female threads, intended for the 2.5 in HEXAFOC focuser.

    Length
    37.5 mm, from the title
    Barrel and thread fittings
    M68 × 0.75 internal and external, as the maker publishes them
    Internal blackening
    Matt black coated against stray light
    Clamping method
    Not published by the maker.
    Rigidity
    Not published by the maker.
    Material
    Aluminium
    Amazon reference
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    EAN
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The rest of this rack

  • NVZPG M48 to M28.5 filter adapter ring

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    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
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    Slot count and filter size
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    Optical path length
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    Manual or motorised operation
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    Light sealing
    Not published by the maker.
    Power
    Not published by the maker.
    Software support
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    Amazon reference
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    EAN
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    Check price on Amazon
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    ZGYDNM M54 filter drawer with two slides

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    Slot count and filter size
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    Manual or motorised operation
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    Light sealing
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    Power
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    Software support
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    EAN
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