Colour Filters – When to use and expected effects
By Greg Walton
| Object | Filter | Result |
|---|---|---|
| Moon | Moon filter | Reduces brightness of the Moon evenly across the spectrum |
| (Neutral density) | Making observations easier without introducing false color | |
| 15 (Deep yellow) | Enhances contrast of lunar surface | |
| 58 (Green) | Like deep yellow, green will enhance contrast and detail in some lunar features | |
| 80A (Light blue) | Reduces glare | |
| Polarizer | Like the neutral density filter, reduces brightness without introducing false colors | |
| Mercury | 21 (Orange) | Helps to make the planet’s phases clearly visible |
| 23A (Red) | Increases contrast of a planet against blue sky, aiding in daytime or bright twilight observation | |
| 25 (Deep red) | Same as #23A, but deeper color | |
| 80A (Light blue) | Improves view of Mercury against bright orange twilight sky | |
| Polarizer | Darkens sky background to increase contrast of planet; helpful for determining phase of Mercury | |
Venum Mars |
25 (Deep red) | Darkens background to reduce glare; some say they also help reveal subtle cloud markings |
| 80A (Light blue) | Improves view of Venus against bright orange twilight sky | |
| Polarizer | Reduces glare without adding artificial color (especially important for viewing the planet through larger telescopes} | |
| 21 (Orange) | Penetrates atmosphere to reveal reddish areas and highlight surface features such as plains and maria (best choice for small apertures) | |
| 23A (Light red) | Same as #21, but deeper color (best choice for medium and large apertures) |
|
| 25 (Deep red) | Same effect as #23A, but deeper color (best choice of the three for very large apertures) |
|
| 38A (Deep blue) | Brings out dust storms on surface of Mars | |
| 58 (Green) | Accentuates melt lines around polar caps | |
| 80A (Light blue) | Accentuates polar caps and high clouds, especially near the planet’s limb | |
| Jupiter | 11 (Yellow-green) | Reveals fine details in cloud bands |
| 21 (Orange) | Accentuates cloud bands | |
| 56 (Light green) | Accentuates reddish features such as the Red Spot | |
| 58 (Green) | Same as #56, but deeper color | |
| BOA (Light blue) | Highlights details in orange and purple belts as well as white ovals | |
| 82A (Very light blue) | Similar effect as #80A, though not as pronounced | |
| Saturn | 15 (Deep yellow) | Helps to reveal cloud bands |
| 21 (Orange) | Similar effect as #11, but deeper color | |
| Comets | SOA (Light blue) | Increases contrast of some comets’ tails |
| Other Uses | 15 (Deep yellow) | Helps block ultraviolet light when doing black-and-white astrophotography |
| 25 (Red) | Reduces impact of light pollution on long-exposure black-andÂwhite photographs taken from light-polluted areas | |
| 58 (Green) | Same as #25; works well for emission nebulae | |
| 82A (Very light blue) | Suppresses chromatic aberration in refractors | |
| Minus Violet | Reduces impact of light pollution without dramatically distorting color; cheaper than broadband LPR filters |