Meade Series 4000 Photo-Visual Color Filters are an essential tool of the lunar and planetary observer, for filters permit the observation and photography of surface detail that is often virtually invisible without filtration.
Meade Filters solve, or greatly reduce the effects of, two basic observing problems: (a) Irradiation is the fuzzying of a boundary between lighter and darker areas of the Moon or a planetary surface and can be caused either by the effects of highly contrasting light impacting the human eye or by the motion of the Earth's atmosphere, through which the observation is being made. (b) Contrast is the separation of adjacent surface regions according to their color; for example, a light green area on Mars can become mixed in the eye with an adjacent light yellow area, to the effect that the combined area appears yellow-green, unseparated into its component regions.
Meade Series 4000 Photo Visual Color Telescope Filters:
- Large 26mm in clear aperture
- Manufactured from the purest crown optical glass
- Dyed-in-the-mass (not "color coated")
- Each filter glass is anti-reflection coated on both sides and is mounted in a machined aluminum cell with the Wratten No. of the filter marked on the side of the cell.
- Filters may be piggybacked, or stacked, to achieve selective filtration of the visual color spectrum.
For visual applications Meade Color Series 4000 Filters thread into the barrels of all Meade 1.25" eyepieces , and into the barrels of virtually all other 1.25 " eyepiece brands as well. The eyepiece-with-filter can be placed in the eyepiece-holder of a Schmidt-Cassegrain telescope or Meade ED Apochromatic Refractor for Tele-Extender eyepiece -projection photography of the Moon and planets. The filters also thread into the barrels of the Meade Camera Adapter (1.25") and Variable-Projection Camera Adapter.
Each Series 4000 Filter is packed in a foam-fitted plastic case for secure long-term storage. Filters may be purchased either individually.
1) Meade Series 4000 Photo-Visual Color Filter Set #1 (item 07530) includes #12, # 23A, #58, # 80A Meade filters:
- # 12 Yellow 07511 (74% transmission): Contrasts strongly with blue-colored features on Jupiter and Saturn, while enhancing red and orange features. Lightens red-orange features on Mars, while reducing or blocking the transmission, and thereby increasing the contrast, of blue-green areas. Useful in increasing the contrast of lunar features in telescopes 6" aperture and larger.
- #23A Light Red 07514 (25% transmission): On telescopes of 6" aperture and larger the #23A does approximately the same functions as the #21 filter, but with stronger contrast and enhancement of marginally defined bluegreen surface detail. Useful primarily on Jupiter, Saturn, and Mars. Increases contrast between Mercury and bright blue sky during daylight observations or during twilight.
- # 58 Green 07517 (24% transmission): Use on telescopes 8" aperture and larger to reject blue- and red-toned structures on the surface of Jupiter and thereby increase their contrast relative to lighter parts of the disc. Also use for the enhancement of Saturn's cloud belts and polar regions. Strongly increases contrast of Mars' polar ice caps, and increases contrast of atmospheric phenomena on Venus.
- # 80-A Blue 07518(30% transmission): A popular filter for the study of Jupiter and Saturn. Enhances contrast of rilles and festoons in Jupiter's cloud belts, as well as details of the Red Spot. Brings out detail in Saturn's belts and polar phenomena. Very useful as a contrast-enhancing lunar filter.
2) Meade Series 4000 Photo-Visual Color Filter Set #2 (item 07529) includes #11, # 25A, #47, # 82A Color Meade Filters:
- # 11 Yellow-Green 07513(78% transmission): Contrasts well with the red and blue characteristics of surface features on Jupiter and Saturn. Darkens the maria visible on Mars, and clarifies the Cassini division in Saturn's rings.
- # 25A Red 07515 (14% transmission): The #25-A filter strongly blocks the transmission of blue and blue-green wavelengths, resulting in very sharply defined contrast between, for example, blue-tinted cloud formations on Jupiter and the lighter-toned features of the disc. Also useful for the delineation of the Martian polar ice caps and maria. Because of its relatively low total light transmission the # 25 A filter should be employed on telescopes of 8" aperture and larger.
- # 47 Violet 07516(3% transmission): Strongly rejects red, yellow, and green wavelengths; useful for the study of Martian polar cap regions and for the observation of occasional phenomena in the upper atmosphere of Venus. Enhances contrast between the rings of Saturn. Use only on telescopes of 8" aperture and larger.
- # 82-A Light Blue 07521(73% transmission): Useful on the Moon, Mars, Jupiter, and Saturn, this subtle pale blue filter enhances areas of low contrast while avoiding significant reduction of overall image brightness. A valuable filter to piggyback with other filters.