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Brand

Seben

Entry-level optics, plainly described

A small range, clearly bounded

Four products, each at the inexpensive end of its shelf. What they have in common is that their listings tell you what they are not: the star diagonal states outright that it suits refractors, Schmidt-Cassegrains and Maksutovs but not Newtonians.

Why that counts here

A negative compatibility statement is rarer than a positive one and worth more. A diagonal that cannot be used on a Newtonian is a fact that saves a return; most listings leave it to be discovered.

The telescope

The Star Sheriff 114/1000 sits on an EQ-3 class mount. Its aperture and focal length are published; the mount is the part to weigh, because a long tube asks more of it than the price suggests.

Reading a Seben page here

The compatibility sentence is the specification. Read it before the optical description.

Seben in this catalogue

Everything Seben puts on these shelves

  • Seben AP3 90 degree 1.25 inch star diagonal

    Seben AP3 90° star diagonal 1.25 in

    A 90-degree star diagonal with a 1.25 in fitting at both ends, explicitly excluded by the maker from use on Newtonian telescopes.

    Mirror or prism construction
    90-degree star diagonal · Not described — neither mirror nor prism is specified
    Reflectivity
    The listing does not carry it
    Barrel size
    31.7 mm (1.25 in) on both sides
    Clamping method
    Not published by the maker.
    Optical path length
    Not published by the maker.
    Build
    Refractors, Schmidt-Cassegrains and Maksutovs, as the maker lists them · Newtonian telescopes, stated outright by the maker
    Amazon reference
    B07NPC3SBN (same reference on 5 Amazon marketplaces)
    EAN
    4049467616306
    • The maker names both what it suits and what it does not, which is rare and useful
    • The least expensive diagonal on this shelf by a considerable margin
    • Neither the optical element nor its coating is described

    Best for: Replacing a missing or broken diagonal on a small refractor at minimum cost

    ≈ £6 / €6
    Check price on Amazon
  • Seben LK1 laser collimator with metal housing

    Seben LK1 laser collimator

    A 1.25 in laser collimator in a metal housing for aligning Newtonian reflectors, with no wavelength, power or adjustment detail published.

    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
    Neither is published
    Target visibility
    Not published by the maker.
    Build
    Not mentioned
    Suitable telescopes
    Newtonian reflectors, per the maker
    Amazon reference
    B006FGYWM0 (same reference on 5 Amazon marketplaces)
    EAN
    4250403200408
    • A metal housing rather than plastic at a low price
    • The one job it is for is stated clearly
    • No wavelength, no output power and no battery type

    Best for: A first collimator where price decides and the tool will be checked on arrival

    ≈ £26 / €29
    Check price on Amazon

Any figure written into the body of this page was true on the day it was written. The amount shown next to each instrument is requested from the retailer as the page loads, and it is that amount, not the text, that stands.