Each color suppresses a contrast so another one shows

The best color planetary filters for 2026

A colored 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-gray 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 color 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 color raises, aperture suitability, set contents and thread size.

By Jean-Benoit Buisson