Meade Coloured Filters
Eyepiece filters are an invaluable aid in lunar
and planetary observing. They reduce glare and light scattering, increase
contrast through selective filtration, increase Meade Series 400W Photo-Visual
Color Filters
For increased contrast and resolution of the Moon
and planets in visual or photographic applications. 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.
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) (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.
The use of a Meade Series 4000 color filter can
mean the difference between seeing small craterlets on the floor of Clavius
on the Moon and not; it can mean the difference between seeing five or
six whirls, festoons, and loops in Jupiter’s north equatorial belt and
seeing one or two; it can mean the difference between seeing the inner
crepe ring of Saturn and not. Depending on atmospheric conditions on both
the Earth and the planet being observed, the advantages of color filters
can be anywhere from subtle to dramatic.
Meade Series 4000 filters are a large 26mm in clear
aperture and are manufactured from the purest crown optical glass, dyed-in-the-mass
(not “color coated”); there are no finer filters available for telescopic
applications. 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 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 (p. 115) 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 foam fitted
plastic case for secure long-term storage.
Recommended Series 4000 Filter Applications
#8 Light Yellow (83% transmission): Useful
in observing red and orange-colored phenomena in the belts of Jupiter and
in enhancing the level of observable detail of small orange-red zonal features
within the belts of the planet- Increases contrast of maria on Mars. Car
result in improved resolution of dusky detail on Uranus and Neptune in
instruments of 10” aperture and larger. A popular filter for the enhancement
of lunar features, particularly in telescopes of 8’ aperture and smaller.
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the Meade #8 Series 4000 Filter Now
#11 Yellow-Green (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.
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the Meade #11 Series 4000 Filter Now
#12 Yellow (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.
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the Meade #12 Series 4000 Filter Now
#21 Orange (46% transmission): Reduces or
blocks transmission of blue-green wavelengths. Use on Jupiter and Saturn
to enhance detail in the belts and polar regions. Sharpens boundaries between
yellow-orange areas and blue-green regions on Mars, resulting in a darkening
of edge-detail in the maria.
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the Meade #21 Series 4000 Filter Now
#23A Light Red (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 blue-green surface detail. Useful primarily on Jupiter, Saturn,
and Mars. Increases contrast between Mercury and bright blue sky during
daylight observations or during twilight.
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the Meade #23A Series 4000 Filter Now
#25 Red (14% transmission): The #25A 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 #25A filter should be
employed on telescopes of 8” aperture and larger.
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the Meade #25 Series 4000 Filter Now
#38A Dark Blue (17% transmission): A popular
filter for the study of Jupiter’s disc, owing to the filter’s strong rejection
of orange and red wavelengths. Increases contrast between the reddish belt
structures and enhances detail of the Red Spot. Also useful for the study
of isolated phenomena, such as dust storms, on Mars, as well as the belt
structure of Saturn. Increases contrast of subtle cloud markings on Venus.
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the Meade #38A Series 4000 Filter Now
#47 Violet (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.
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the Meade #47 Series 4000 Filter Now
#56 Light Green (53% transmission):
Excellent
for the observation of Martian polar ice caps as well as yellow-tinted
dust storms on the Martian surface. Increases contrast of the red and blue
regions in Jupiter’s atmosphere as well as in the cloud belts. Also useful
for enhancing lunar detail.
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the Meade #56 Series 4000 Filter Now
#58 Green (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.
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the Meade #58 Series 4000 Filter Now
#80A Blue (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.
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the Meade #80A Series 4000 Filter Now
#82A Light Blue (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.
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the Meade #82A Series 4000 Filter Now
ND 96 Moon Filter (0.9 density; 13% transmission):
The neutral density filter transmits light uniformly across the entire
visual spectrum. It serves as an excellent filter to reduce glare and irradiation
when observing the Moon with any telescope 4” and larger. The ND96 filter
may also be employed in the splitting of close double stars where one of
the binary pair significantly exceeds the other in brightness.
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the Meade #ND96 Series 4000 Filter Now
Meade Series 4000 Photo-Visual Color Filters
may be ordered individually or in the following sets:
Set #1 (4 filters): #12 Yellow; #23A Light
Red; #58 Green; #80A Blue. Buy
the Meade Series 4000 Filter Set 1 Now
Set #2 (4 filters): #11 Yellow-Green; #25A
Red; #47 Violet; #82A Light Blue. Buy
the Meade Series 4000 Filter Set 2 Now
Set #3 (4 filters): #8 Light Yellow; #21
Orange; #38A Dark Blue; #56 Light Green. Buy
the Meade Series 4000 Filter Set 3 Now
#905 Variable Polarizing Filter (1.25”)
For glare-reduction in observing the Moon the #905 Variable Polarizer includes
two Polarizer filters mounted in a specially-machined cell. The #905 permits
variable settings of the light transmission between 5% and 25%, to account
for varying lunar surface brightness according to the phase of the Moon
and the magnification and aperture of the telescope. Accepts 1.25” eyepieces.
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the Meade Series 4000 #905 Filter Now
MOON FILTERS
Moon Filters are economical eyepiece filters for
reducing the brightness of the moon and improving contrast, so greater
detail can be observed on the lunar surface. The clear aperture is 21mm
for the 1 1/4" filter and 10mm for the .96" filter. Transmission is about
18%.
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