Lumicon 2" OIII Filter
About the Lumicon OIII Filter
The Lumicon OIII (Oxygen III) filter isolates just the two doubly ionized oxygen lines (496 and 501nm lines) emitted by diffuse, planetary and extremely faint nebulae. By allowing this narrow-band of light pass through, you will notice a tremedous increase in contrast and brightness in these typically faint objects. These qualities also make it a great choice for light-polluted skies. An excellent addition to your observing arsenal, the 48mm version easily threads into your two inch accessories. Objects like the Lagoon, Swan, Dumbbell, Ring and Veil nebulae will be tremendously enhanced with the OIII filter, particularly under light polluted skies.
Using thin-film dielectric coatings on optically flat glass, over 30 layers of different coating material are what make up Lumicon's narrow band filter series. This method and the material used provide a very hard coated surface that resists hairline scratches and dings exceptionally well. Consisting of two elements which sandwich these coatings, an anti-reflection coating is added to prevent ghosting.
Optimum Exit Pupil
Exit pupil is highly dependant on the equipment you're using. Each Lumicon filter has an optimum exit pupil for peak performance. By dividing the focal ratio of your telescope into your eyepiece's focal length, you are provided with the exit pupil measurement. For example, an f/8 telescope using a 32mm eyepiece has an exit pupil of 4mm. At 10-12nm bandpass, the OIII filter's best exit pupil range is 2-5mm under light polluted skies and 3-7mm under dark sky conditions.
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