Skip to content

Thread adapters

Omegon M48 to T2 adapter, low profile (49749)

A short adapter converting an M48 internal thread to a T2 external thread, with the maker emphasising that its low profile avoids focus problems.

Omegon low-profile M48 to T2 adapter ring

Omegon M48 to T2 adapter, low profile (49749)

A short adapter converting an M48 internal thread to a T2 external thread, with the maker emphasising that its low profile avoids focus problems.

Slot count and filter size
M48 female · T2 male — that is M42 × 0.75
Optical path length
Very low, as the maker states it; no figure is given
Manual or motorised operation
A thread adapter — no optics, and not a filter wheel
Light sealing
Not published by the maker.
Power
Not published by the maker.
Software support
Not published by the maker.
Amazon reference
B01KPR3X1K (same reference on 6 Amazon marketplaces)
EAN
4049467497493
  • The maker addresses back focus directly rather than leaving it to be discovered
  • A named list of what it is meant to connect, which most adapter listings omit
  • “Very low” is not a millimetre figure

Best for: Bringing a 2 in filter thread onto a T2 camera fitting with minimal focus loss

≈ £19 / €19
Check price on Amazon

Specifications

Slot count and filter size
M48 female · T2 male — that is M42 × 0.75
Optical path length
Very low, as the maker states it; no figure is given
Manual or motorised operation
A thread adapter — no optics, and not a filter wheel
Light sealing
Not published by the maker.
Power
Not published by the maker.
Software support
Not published by the maker.
Amazon reference
B01KPR3X1K (same reference on 6 Amazon marketplaces)
EAN
4049467497493

The conversion most imaging trains need

M48 is the thread of 2 in filters and of the larger imaging components. T2 is what most camera adapters carry. Bridging the two is one of the two commonest adapter problems in astrophotography, and this ring does it in one piece.

Why the maker talks about focus

Because it is the right thing to talk about. An adapter contributes nothing optically and costs back focus, and the difference between a five-millimetre ring and a fifteen-millimetre one decides whether a reducer can be spaced correctly. Omegon says “very low” without printing a number.

What it connects, named

Crayford focusers, apochromats, eyepieces, filter wheels and coma correctors. Listing the intended partners is more useful than a generic compatibility claim, and few adapter listings bother.

The narrowing

Going down from M48 to T2 reduces the clear aperture. For a small sensor that is invisible; for a large one it is the limiting element in the train, and no adapter can change that.

Availability

German, French, Italian and Spanish Amazon stores ran from 19 € to 22 € 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 filter wheels

  • ZGYDNM M54 filter drawer with two filter slides

    ZGYDNM M54 filter drawer with two slides

    A filter drawer rather than a wheel: two slides carry the filters, and the body threads M54 × 0.75 at both ends.

    Slot count and filter size
    M54 × 0.75 at the telescope end and M54 × 0.75 at the output · Two
    Optical path length
    4 mm is given for the interface and 16 mm as the extended length; both are reproduced as published
    Manual or motorised operation
    A filter drawer — the filters slide in and out, they do not rotate
    Light sealing
    Not published by the maker.
    Power
    Not published by the maker.
    Software support
    Not published by the maker.
    Amazon reference
    B0DK5TJY4G (same reference on 5 Amazon marketplaces)
    EAN
    9106666473491
    • A drawer consumes far less optical path than a wheel
    • Two slides mean a filter can be swapped in seconds without unthreading anything
    • The listing gives two different thickness figures without saying which is which

    Best for: A short back-focus imaging train where a wheel would not fit

    ≈ £61 / €72
    Check price on Amazon
  • Astromania five-position 2 inch filter wheel

    Astromania 2 in five-position filter wheel (FW2M5)

    A manual filter wheel holding five 2 in filters in an aluminium body, with a 2 in adapter on the telescope side and T-2 and M48 threads on the camera side.

    Slot count and filter size
    Five, numbered 1 to 5 · 2 in (5.1 cm) standard filters · T-2 and M48, as the maker states them
    Optical path length
    The focuser must travel about 20 mm further inward than normal, as the maker states it
    Manual or motorised operation
    A filter wheel — the only one in this group · Supplied with a 2 in adapter for the focuser
    Light sealing
    Aluminium, described by the maker as suitable for heavy cameras
    Power
    Not published by the maker.
    Software support
    Not published by the maker.
    Amazon reference
    B0140UA9F6 (same reference on 6 Amazon marketplaces)
    EAN
    6970019290355
    • Publishes the 20 mm of inward focus it consumes, which is the figure that decides whether it works at all
    • Two accessory threads — T-2 and M48 — cover most imaging trains
    • Twenty millimetres of inward focus is more than some refractors have to give

    Best for: A Newtonian or Dobsonian imaging train where back focus is short and filters change often

    ≈ $91 / £95 / €105
    Check price on Amazon
  • ASToptics M54 male to T2 female adapter

    ASToptics M54 male to T2 female adapter (57801)

    A thread adapter from M54 male to T2 female, whose entire listing consists of generic statements about quality.

    Slot count and filter size
    M54 male, from the title · T2 female, from the title · Not stated for either thread
    Optical path length
    The listing gives none
    Manual or motorised operation
    A thread adapter — no optics, and not a filter wheel
    Light sealing
    Not stated
    Power
    Not published by the maker.
    Software support
    Not published by the maker.
    Amazon reference
    B0BPXFY2VT (same reference on 5 Amazon marketplaces)
    EAN
    4049467578017
    • M54 to T2 is a conversion the larger imaging trains genuinely need
    • From a maker whose range is sold through astronomy specialists
    • Five bullets and not one measurement, material or figure among them

    Best for: An M54 imaging train that has to meet a T2 camera fitting

    ≈ £36 / €39
    Check price on Amazon

The rest of this rack

  • SVBONY 0.5x focal reducer with C-mount adapter

    SVBONY 0.5x reducer with C-mount adapter (SV0.5x)

    A fully multi-coated 0.5x reducer for 1.25 in fittings, supplied with a C-mount adapter for cameras that use that thread.

    Reduction factor
    0.5x, from the title
    Required back focus
    Neither is published
    Image circle
    Not published by the maker.
    Corrector function
    Focal reducer with optics
    Thread standards
    1.25 in (3.2 cm), from the title
    Vignetting
    Not published by the maker.
    Housing
    Fully multi-coated, from the title
    Amazon reference
    B0792XJWFS (same reference on 1 Amazon marketplace)
    EAN
    0609378745560
    • The C-mount adapter suits the small cameras that C-mount threads are found on
    • Fully multi-coated is claimed, which is the strongest of the four coating labels
    • The listing has no description whatsoever beyond its title

    Best for: A small sensor camera with a C-mount thread on a long-focal-length telescope

    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
  • 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

All filter wheels