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Full aperture, in front of the telescope, and nowhere else

The best solar filters for 2026

A solar filter is fitted in front of the telescope, covering the full aperture, so that the great majority of the light is rejected before it ever enters the tube. That is the only arrangement any maker of these products describes, and the instructions supplied with the filter and with the telescope are where the conditions of use are set out — not here, and not in a comparison table. The screw-in filters that fitted the eyepiece end of older telescopes are not part of this shelf, and the reason is worth stating plainly: they thread in where the telescope concentrates the light, and makers withdrew them because that concentrated heat can crack the glass. Current manufacturers and observing organisations publish the same position — do not use one. What can usefully be compared is construction. A film filter uses a coated polymer sheet held in a cell; it is light, it does not unbalance a tube, and the better films deliver a neutral or bluish disc that shows granulation well. A glass filter is heavier, more rigid, and usually gives a yellow or orange disc that many observers find more natural. Both are made in the same range of apertures, and the fit matters: the cell has to sit on the tube without play, because a filter that can be knocked loose is the single failure mode every maker warns about, and most now add a set screw or a tightening band for exactly that reason. Read the standard the listing cites and the maker’s own inspection instructions before every use. Read the aperture of the cell against the outside diameter of the tube, which is not the same as the aperture of the optics. We compare cell fit and outside diameter, film or glass construction, cited standard, mounting security, image colour and supplied storage.

The parts here, column by column

  1. Astromania Deluxe 100 mm full-aperture solar filter cell

    Astromania Deluxe Solar Filter 100 mm

    A full-aperture solar filter with a Baader AstroSolar film in an anodised aluminium cell, clamped to the front of the tube by three padded screws.

    Cell fit and outside diameter
    100 mm, as the maker states it · 75 mm, as the maker states it · 70 mm to 92 mm, as the maker states them
    Film or glass construction
    Full-aperture filter — it fits over the front of the telescope · Baader AstroSolar, named by the maker · Anodised aluminium with three clamping screws and protective plastic caps
    Cited standard
    99.9 % of incoming sunlight, as the maker states it · ISO 12312-2:2015 — a document whose own title covers filters for direct observation of the Sun by the unaided eye
    Mounting security
    Not published by the maker.
    Image colour
    Not published by the maker.
    Supplied storage
    Not published by the maker.
    Amazon reference
    B07439W4R8 (same reference on 6 Amazon marketplaces)
    EAN
    6970019299129
    • Three published diameters — 100 mm outer, 75 mm inner, 70 to 92 mm tube range — rather than one vague size
    • An aluminium cell holds the film flat, which matters more than the film’s brand
    • A tube at the very edge of the 70–92 mm range sits less securely than one in the middle

    Best for: Fitting the front of a telescope whose tube outside diameter has been measured first

    ≈ $35 / £37 / €45
    Check price on Amazon
  2. Omegon full-aperture solar filter in its moulded plastic frame

    Omegon Solar filter for 114 mm telescopes

    A full-aperture solar filter supplied ready-mounted in a moulded plastic frame with an ND5 solar film, made to push directly onto Omegon Basic telescopes.

    Cell fit and outside diameter
    Omegon Basic telescopes, 114 mm; the maker adds “or comparable models” · The listing gives none as a figure
    Film or glass construction
    Full-aperture filter — it fits over the front of the telescope · Solar film with a filter factor of ND5, as the maker states it · Moulded plastic, supplied already assembled
    Cited standard
    Not published by the maker.
    Mounting security
    None, per the maker
    Image colour
    Not published by the maker.
    Supplied storage
    Not published by the maker.
    Amazon reference
    B012FT844C (same reference on 5 Amazon marketplaces)
    EAN
    4049467457879
    • Supplied ready-assembled, so there is no film to cut or mount
    • The film density is named as ND5 rather than described
    • No tube outside diameter figure is published — only a model family

    Best for: An Omegon Basic 114 mm, or a tube whose front diameter has been checked against one

    ≈ £28 / €29
    Check price on Amazon
  3. GMBYLBY solar film sheet for telescope apertures

    GMBYLBY Solar film sheet 80–250 mm

    A sheet of solar filter film covering telescope apertures from 80 to 250 mm, sold as material to be mounted by the buyer.

    Cell fit and outside diameter
    80 to 250 mm, from the title
    Film or glass construction
    Solar film sold as a sheet — mounting is the buyer’s job · The listing gives none anywhere in the listing
    Cited standard
    Not published by the maker.
    Mounting security
    Not published by the maker.
    Image colour
    Reddish-yellow Sun, as the maker states it
    Supplied storage
    Not published by the maker.
    Amazon reference
    B0HD5JWVZL (same reference on 1 Amazon marketplace)
    EAN
    7750300370749
    • A sheet covers a range of apertures rather than one tube
    • Film is the least expensive way to cover a large aperture
    • No optical density figure is published, which is the defining specification of solar film

    Best for: Somebody equipped to build and check a filter cell themselves

    ≈ €30
    Check price on Amazon
  4. ZBIianxer solar film sheet for telescope use

    ZBIianxer Solar film sheet

    A solar film sheet sold on portability, with neither an aperture range nor an optical density anywhere in the listing.

    Cell fit and outside diameter
    The listing gives none anywhere in the listing
    Film or glass construction
    Solar film sold as a sheet — mounting is the buyer’s job · The listing gives none anywhere in the listing
    Cited standard
    Not published by the maker.
    Mounting security
    Not published by the maker.
    Image colour
    Reddish-yellow Sun, as the maker states it
    Supplied storage
    Not published by the maker.
    Amazon reference
    B0H4DKVQW1 (same reference on 6 Amazon marketplaces)
    EAN
    7614593103883
    • Film can be cut to whatever aperture the buyer needs
    • The maker mentions cleaning with a cloth or water, which most film listings do not
    • Neither a size nor a density is published — two omissions where one would be too many

    Best for: Nobody who has not already decided what density and size they need

    ≈ €53
    Check price on Amazon
  5. ihwfaityu 140 mm solar film sheet

    ihwfaityu Solar film sheet 140 mm

    A solar film sheet of 140 mm, sold as material for mounting, with a size in the title and no density figure anywhere.

    Cell fit and outside diameter
    140 mm, from the title
    Film or glass construction
    Solar film sold as a sheet — mounting is the buyer’s job · The listing gives none anywhere in the listing
    Cited standard
    Not published by the maker.
    Mounting security
    Not published by the maker.
    Image colour
    Reddish-yellow Sun, as the maker states it
    Supplied storage
    Not published by the maker.
    Amazon reference
    B0HFJK63DD (same reference on 1 Amazon marketplace)
    EAN
    8003890012148
    • A size is published, which one of the three identical listings manages and another does not
    • 140 mm covers the aperture of most beginner reflectors with margin for a cell
    • No optical density figure, which is the defining property of a solar film

    Best for: Covering a telescope of about 130 mm aperture, by somebody who will build the cell

    ≈ €36
    Check price on Amazon
  6. POFET 1 inch eyepiece-end solar filter in aluminium cell

    POFET Eyepiece-end solar filter

    A 1 in aluminium-celled solar filter that screws onto the eyepiece end of the light path rather than over the telescope’s aperture.

    Cell fit and outside diameter
    2.5 cm (1 in), from the title
    Film or glass construction
    Threads onto an eyepiece — it does not fit over the front of the telescope · Aluminium alloy with a standard thread, per the maker · The listing gives none anywhere in the listing
    Cited standard
    The listing gives none anywhere in the listing
    Mounting security
    Not published by the maker.
    Image colour
    Not published by the maker.
    Supplied storage
    Not published by the maker.
    Amazon reference
    B08M9HY7DC (same reference on 5 Amazon marketplaces)
    EAN
    0703355530153
    • An aluminium cell rather than a plastic one
    • A standard thread means it will engage a normal eyepiece barrel
    • No density, no transmission and no waveband figure of any kind is published

    Best for: Nobody, until the manufacturer’s own instructions and specification have been read

    ≈ £7
    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.