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Colour planetary filters

Astro Professional Blue #80A 2 in

A blue planetary filter designated Wratten #80A in a 2 in thread, intended to raise contrast on the Moon and planets.

Astro Professional blue #80A 2 inch planetary filter

Astro Professional Blue #80A 2 in

A blue planetary filter designated Wratten #80A in a 2 in thread, intended to raise contrast on the Moon and planets.

Wratten number
Wratten #80A, blue
Transmission
The listing gives none
The features each colour raises
Raises contrast on lunar and planetary observation
Aperture suitability
Not published by the maker.
Set contents
Not published by the maker.
Thread size
2 in thread
Amazon reference
B007IU98K8 (same reference on 5 Amazon marketplaces)
EAN
4250514801099
  • A Wratten number is the one designation that means the same thing between makers
  • A 2 in thread is uncommon for colour filters and suits wide-field eyepieces
  • No transmission curve or percentage is published

Best for: A larger telescope where a blue filter can afford the light it removes

≈ £24 / €24
Check price on Amazon

Specifications

Wratten number
Wratten #80A, blue
Transmission
The listing gives none
The features each colour raises
Raises contrast on lunar and planetary observation
Aperture suitability
Not published by the maker.
Set contents
Not published by the maker.
Thread size
2 in thread
Amazon reference
B007IU98K8 (same reference on 5 Amazon marketplaces)
EAN
4250514801099

One sentence, and a number that carries it

The listing says that colour filters raise contrast on lunar and planetary observation. That is the whole description. What makes the product identifiable at all is the Wratten designation in its name: #80A, a medium blue.

What the number fixes and what it does not

It fixes the intended transmission colour, which is why two #80A filters from different makers are comparable in a way that two filters called “blue” are not. It does not fix the glass, the coating, the cell depth or the transmission curve.

Aperture decides whether it helps

A blue filter removes the red and much of the green. On a 200 mm telescope there is light to spare and the contrast gain shows; on an 80 mm the image simply darkens. This is the single most important thing to know before buying colour filters.

The 2 in thread

Rarer than 1.25 in for colour filters, and matched to wide-field eyepieces and 2 in diagonals. It also means the filter cannot be moved to a 1.25 in eyepiece without a step ring.

Availability

German, Italian and Spanish Amazon stores ran from 24 € to 28 € on the day of the survey.

British Amazon store lists it in local currency, which the euro range above sets aside.

French 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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    Wratten number
    Not published by the maker.
    Transmission
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    The features each colour raises
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    Aperture suitability
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    Set contents
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    Thread size
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    EAN
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    • The maker describes the effect of each named filter on specific planets
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    Mass
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    Bore diameter
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    Locking method
    Not published by the maker.
    Coating
    Not published by the maker.
    Finish
    Not published by the maker.
    Compatible mounts
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    Overall dimensions
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    Amazon reference
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    EAN
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    Coating
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    Finish
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    Mass
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    Bore diameter
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    Locking method
    A locking screw for a secure seat
    Coating
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    Finish
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    Compatible mounts
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    Overall dimensions
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