Each colour suppresses a contrast so another one shows

The best colour planetary filters for 2026

A coloured filter on a planet does something simple and often misunderstood: by removing part of the spectrum it lowers the brightness of features that reflect that part, and a feature that was lost against a bright background becomes visible against a darker one. Nothing is added. The classification still uses Wratten numbers, a photographic system from long before the hobby adopted it, and those numbers are the only reliable way to compare across makers, since names like light blue are applied loosely. The pairings are well established: a blue filter raises the contrast of the belts of Jupiter and of the polar hazes, a red or orange one darkens the blue-grey regions of Mars and sharpens the boundary of the polar cap, a yellow one tames the glare of Saturn and helps the Cassini division stand out, and a light green one is often used on Jupiter for the Great Red Spot. How much of that is visible at all depends on the aperture, because every filter costs light, and a deep filter in a small telescope leaves too little to see. Filters are sold singly and in sets, and a set is almost always cheaper than three singles while containing at least one colour that never gets used. Read the thread size, read whether the glass is dyed through or coated, and read the cell depth against short eyepiece barrels. We compare Wratten number, transmission, the features each colour raises, aperture suitability, set contents and thread size.

The parts here, column by column

1. 

   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
2. 

   Omegon Colour filter set, 1.25 in, six pieces

   A six-filter 1.25 in colour set for planetary observing, with the maker naming #21 orange and #25 red and describing what each brings out.

   Wratten number

   Not published by the maker.

   Transmission

   The listing gives none for any filter in the set

   The features each colour raises

   Blocks blue and green, raising detail in the belts of Jupiter and Saturn; sharpens boundaries on Mars · Blocks blue and green almost entirely, for very high contrast on Jupiter and Saturn cloud detail

   Aperture suitability

   Not published by the maker.

   Set contents

   Six colour filters; the maker names #21 orange and #25 red

   Thread size

   1.25 in thread

   Amazon reference

   B0017GTVLK (same reference on 6 Amazon marketplaces)

   EAN

   4049467113331

   • Two of the six are named by Wratten number, which makes them comparable
   • The maker describes the effect of each named filter on specific planets
   • Four of the six filters are not identified by number in the listing

   Best for: A planetary observer with a telescope large enough to spend the light

   ≈ £57 / €63

   Check price on Amazon