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A full Moon in a large telescope is genuinely too bright

The best Moon filters for 2026

A full Moon seen through a telescope of any size is uncomfortably bright, and the discomfort is not merely aesthetic: a dazzled eye loses the dark adaptation that took twenty minutes to acquire, and the rest of the session suffers for it. A Moon filter dims the disc so that the low-contrast detail near the terminator becomes readable rather than washed out. The plain versions are a single piece of coated glass with a published transmission percentage, and that figure is what should be compared — a filter that passes a quarter of the light and one that passes half are different tools for different phases and different apertures. Cheap filters achieve the dimming with a green tint, which does the job and colours the Moon; a neutral density filter dims evenly and keeps the grey. The more flexible answer is a variable polarising filter, two polarising elements in a rotating cell that between them cover a wide range of transmission from a single accessory. It suits an observer following the Moon through its phases, where the right amount of dimming changes week by week, and it works on bright planets as well. Read the thread size against the eyepieces in the case, since these screw into the barrel and the two common fittings differ. Read whether the glass is described as flat and whether the cell adds enough length to foul a short eyepiece barrel. We compare transmission percentage, neutral or tinted dimming, fixed or variable design, thread size, glass flatness and cell depth.

The parts here, column by column

  1. Celestron 94107 variable polarising moon filter

    Celestron Variable Polarizing Moon Filter (94107)

    A two-element polarising filter for 1.25 in eyepieces with transmission adjustable from 1 to 40 per cent by rotating its lower ring.

    Transmission percentage
    1 % to 40 %, adjustable, as the maker publishes it
    Neutral or tinted dimming
    Not published by the maker.
    Fixed or variable design
    Variable polarising filter, threaded for 1.25 in eyepieces · Rotate the lower ring, per the maker · Threaded on both faces, so other filters can be combined with it
    Thread size
    Not published by the maker.
    Glass flatness
    Not published by the maker.
    Cell depth
    Not published by the maker.
    Amazon reference
    B07N99RW5K (same reference on 6 Amazon marketplaces)
    EAN
    0050234941075
    • A published transmission range rather than a single fixed figure or a colour word
    • One filter covers what several fixed neutral filters would
    • A polarising pair costs some light even at its most open setting

    Best for: The Moon across its whole cycle, where a fixed filter is right at only one phase

    ≈ $43 / £42 / €38
    Check price on Amazon
  2. Omegon Premium 2 inch moon filter with 25 per cent transmission

    Omegon Premium Moon Filter 25 % 2 in

    A neutral grey Moon filter passing 25 per cent of the light, threaded for 2 in eyepieces, intended to dim the Moon without tinting it.

    Transmission percentage
    25 %, as the maker publishes it
    Neutral or tinted dimming
    Neutral — the Moon keeps its natural appearance, per the maker
    Fixed or variable design
    Neutral grey filter, threaded for 2 in eyepieces
    Thread size
    2 in filter thread
    Glass flatness
    Not published by the maker.
    Cell depth
    Not published by the maker.
    Amazon reference
    B018TN4TCO (same reference on 6 Amazon marketplaces)
    EAN
    4049467474043
    • The transmission is published as a percentage rather than a word
    • Neutral rather than tinted, so lunar colour is not altered
    • A single fixed value suits one range of phases and apertures

    Best for: A wide-field 2 in eyepiece used on the Moon at first or last quarter

    ≈ €39
    Check price on Amazon
  3. Vixen 1.25 inch moon filter

    Vixen Moon filter 1.25 in (37222-5)

    A plane-parallel Moon filter that screws into 1.25 in eyepieces, sold on the quality of its substrate rather than on a stated transmission.

    Transmission percentage
    The listing gives none anywhere in the listing
    Neutral or tinted dimming
    Not published by the maker.
    Fixed or variable design
    Moon filter, threaded for 1.25 in eyepieces
    Thread size
    Not published by the maker.
    Glass flatness
    High-quality plane-parallel glass, as the maker states it
    Cell depth
    Not published by the maker.
    Amazon reference
    B0018HILMI (same reference on 6 Amazon marketplaces)
    EAN
    4955295372225
    • Plane-parallel glass is the property that keeps the image sharp at high magnification
    • A 1.25 in thread fits the eyepiece size almost everyone owns
    • No transmission percentage, so it cannot be compared with the filters beside it

    Best for: A 1.25 in eyepiece case where substrate quality matters more than a published figure

    ≈ $54 / £42 / €45
    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.