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Nebular Filters
Nebular
filters are designed to select specific frequencies of light while
blocking others. For instance, an anti-light pollution filter will
block the frequencies of light produced by mercury and sodium vapor
street lights. This will not make the nebulae and galaxies brighter,
but it will make the sky around them darker thus increasing contrast.
Lumicon's Deep Sky, Hydrogen-Beta, Oxygen III, and Ultra High Contrast
Filters are the result of 20 years of steady design improvements,
and continue to deliver the highest performance of all anti-light
pollution filters obtainable today. The following information recommends
which filter to use on which celestial objects, and explains how filter
transmissions differ. |
| Objects | Examples | Best Filter for Viewing | Best Filter for Photography |
| Stars
& Star Clusters | M13,
M11 | Deep
Sky | Deep
Sky |
| Diffuse
Nebulae | Lagoon,
Swan | OIII
(light polluted sky),
Deep Sky,
UHC (dark sky) | Deep
Sky |
| Planetary
Nebulae | Dumbbell,
Ring | OIII
(light polluted sky),
Deep Sky,
UHC (dark sky) | Deep
Sky |
| Faint
Planetary Nebulae | NGC
7293,
Abell 33,
Jones 1 | OIII | Deep
Sky |
| Reflection
Nebulae | Pleiades,
Trifid | Deep
Sky | Deep
Sky |
| Spiral
Galaxies | M33,
M101 | Deep
Sky | Deep
Sky |
| Faint
Nebulae | Veil,
Rosette,
N. American | OIII
(light polluted sky),
Deep Sky,
UHC (dark sky) | Deep
Sky |
| Extremely
Faint Nebulae | California,
Horsehead | H-Beta | Night-Sky
H-Alpha
Deep Sky |
Anti-Light Pollution (ALP) Filter
- Intended for viewing nebulae from light-polluted skies.
- Blocks all mercury vapor and high & low pressure sodium vapor lamp light, neon lights and airglow, while transmitting the rest of the visible spectrum.
- The best all-around visual light pollution filter for use under urban skies.
- This filter also provides high-contrast views of the Martian polar caps
The Lumicon Deep Sky Filter
The
Deep Sky Filter is basically a general-purpose light pollution filter that restores
a dark sky background for viewing and photographing deep sky objects from cities.
It is the best light-pollution filter for all astrophotography on the market today. Visually,
the Deep Sky Filter is the most useful filter under light-polluted skies, from
where it reveals star clusters, galaxies and nebulae. Photographically,
the Deep Sky Filter enables deep sky photographs to be taken from cities, and
it blocks some of the natural airglow at dark-sky sites, thus improving deep-sky
photographs taken from those locations. Mercury
light pollution occurs at 365, 405, 436, 546, 577, and 617nm. High-pressure sodium
streetlights emit at 570, 583, 600, and 617nm. The Lumicon Deep Sky Filter blocks
all of these. |
Ultra High Contrast (UHC) Filter
- Narrow band pass filter (24nm) isolates the two doubly ionized oxygen lines (496 and
501nm) and the hydrogen-beta line (486nm) emitted by planetary and most emission
nebulae.
- Provides superb views of the Orion, Lagoon, Swan and other extended nebulae.
- The best all-around dark-sky nebular filter available.
| The
Lumicon UHC FilterThe
UHC filter is THE all-around nebular filter. It specializes in showing nebulosity,
even outperforming the Deep Sky Filter in this one application under suburban
skies. The UHC filter is a visual-use-only filter, but it can be used in this
capacity to great advantage from both suburban and dark-sky sites. You would purchase
the OIII and H-Beta filters separately only for specialized high-contrast and
comparison viewing of certain nebulae. |
Oxygen-III (O-III) Filter
- Narrow
bandpass filter (11nm) isolates just the two doubly ionized oxygen lines (496nm
and 501nm) emitted by planetary and extremely faint nebulae.
- Produces near-photographic views of the Veil, Ring, Dumbbell, Orion, and many other nebula.
| The
Lumicon O-III FilterThe Oxygen III Filter is for visual use only. The reason is that the filter's narrow
bandpass is located at the intersection of the filter's two concave-downward graphs
of transmission in blue and green light. At this wavelength, the human eye is
actually more sensitive than photographic film. For photography of planetary nebulae,
use the broad-band Lumicon Deep Sky Filter. |
Hydrogen-Beta (H-Beta) Filter
- Extremely narrow bandpass filter isolating the hydrogen-beta line alone (486nm).
- Excellent for viewing the Horsehead, Cocoon and California Nebulae.
- Is often the only way to view certain nebulae.
- It is best used under clear skies with large aperture telescopes.
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