Lumicon Nebula Filters

The 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.

Ideal for Photographic Applications

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Ideal for Visual Usage

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Infrared Blocking Filters

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Minus Violet Filters

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Deep Sky 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 in urban skies.

- This filter also provides high-contrast views of the Martian polar caps

Ultra High Contrast 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.

Oxygen III Filter

- Narrow band pass 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, plus many other nebula.

- Hydrogen-Beta Filter

- Extremely narrow bandpass filter isolating the hydrogen-beta line alone (486nm).

- Excellent for viewing the Horsehead, Cocoon and California Nebulae.

- Often the only way to view certain nebulae.

  - It is best used under clear skies with large aperture.

Comet Filter

- Designed to enhance the cyanogen (CN) frequency found in comet tails..

Exit Pupil Specifications:

The exit pupil of a telescope is a measure of specific magnification, which differs from absolute magnification, and which determines the surface brightness of an extended object image. Exit pupil diameter may be expressed as the quotient of eyepiece focal length divided by the telescope's focal ratio. For example, a 32mm eyepiece used on an f/10 telescope will have a 3.2mm exit pupil. Each Lumicon filter has an optimum eyepiece exit pupil range shown below.

Notice:

As filter bandpass decreases, optimum exit pupil size tends to increase. To determine the best eyepiece focal length to use with a given filter, simply multiply the Exit Pupil value shown above by your telescope's focal ratio. For example, if you are using the Lumicon H-Beta filter at a dark site and your telescope has an f/6 focal ratio, the best range of eyepiece focal lengths to use with this filter is [(4 to 7) x 6] = 24mm to 42mm.

Filter Construction:

Lumicon nebula filters are made using thin-film dielectric coatings on optically flat glass. These exclusively designed dielectric coatings consist of over 30 alternating layers of several different materials. Each layer is about a wavelength of light thick and has a thickness accurate to 2 - 3 angstroms. Lumicon nebula filters include anti-reflection coatings on both sides to prevent ghosting and increase light transmittance. They also have a hard, electron-beam deposited coating for mechanical protection. While still delicate, Lumicon filters may be carefully cleaned with isopropyl alcohol, or Lumicon’s Advanced Cleaning Kit

Mechanical Design:

These filters thread directly into most eyepieces and telescope accessories. Threads are standard for 1" filters. 48mm filters are standard for 2" O.D. eyepieces.

Bandpass:

These Lumicon filters reject man-made and natural light pollution. Mercury light pollution occurs at 365, 405, 436, 546, 577, and 617nm. High-pressure sodium streetlights emit at 570, 583, 600, and 617nm. Natural airglow occurs at 558 and more weakly at 630nm. There is a window of greatly reduced light pollution from 440nm (blue) to 540nm (green). The Lumicon Deep Sky Filter has a wide 90-100nm bandpass for most of this range (441-535nm) to yield maximum transmission of light from stars and galaxies. The UHC Filter has a narrow 22nm bandpass through 484-506nm. The OIII Filter has a very narrow 11nm bandpass for 495-501nm, and the H-beta Filter has the narrowest bandpass of all - only 8nm centered at 486nm. The narrower the bandpass, the higher the rejection of light pollution and the blacker the skies. However, a narrower bandpass also means fainter star images. Nevertheless, the Deep Sky Filter has high transmission for the photographic red nebula emission lines.

Nebula Emission Lines:

The main visible radiation from emission nebulae consists of doubly ionized oxygen near the wavelength of 500nm. There is also weaker emission due to hydrogen-beta at 486nm. The invisible but photographically important emission of red hydrogen-alpha and ionized nitrogen occur near 657nm.

Best Nebula Filters - For Selected Objects