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Planetary nebulae and some emission nebulae emit light also at a particular wavelength, 501 nm. This line, called O-III (doubly ionized oxygen) is particularly useful for astronomical photography since it can be studied with special filters that isolate it from the rest of the electromagnetic spectrum. This is precisely the action of our filter O-III CCD 12nm.
Photographic use: as with H-alpha filters, this filter dramatically increases the contrast of the image as the background sky turns black and make appear areas and details of the nebulae that are not visible without a filter. The filter also decreases the size of the stars highlighting even more nebulae. The O-III CCD 12nm filter can be used with H-alpha and SII CCD 12nm filters to "reconstruct" color images of deep sky objects that emit light in specific wavelengths, such as gas nebulae. In fact you can take a picture for each different filter and use a special processing software (indicating that each filter corresponds to one of the R, G and B channels) to get the color image. This technique is very useful to use monochrome CCD cameras for color images even from places with strong light pollution.
This filter is also perfect for use with achromatic or semi-apochromatic refractors that, because of the chromatic aberration, are not usually indicated for the long-exposure photography. But, using this filter the deep-sky photography becomes not only possible but also provides excellent results since the narrow bandwidth practically cancels the effect of chromatic aberration.
Visual use: because of the very narrow bandwidth, the light that reaches the eye is strongly attenuated so this filter is not suitable for use visual, unless using large diameter telescopes, at least 35cm.
It selects only the O-III line (501nm)
It cancel the light pollution, making dark the sky background
Transmittance higher than 85% at 501nm
Anti-reflective multi-layer coating
Quality substrate not to introduce aberrations in the images
Available in 2 versions: 31.8mm (1.25") and 50.8mm (2") diameter
How to use the filters:
Our filters are always available in 2 diameters: 31.8mm and 50.8mm. These standards are commonly used by telescopes and their accessories. For example, depending on their function, they can be used with a CCD ora A DSLR camera (using appropriate photo adapters), but also screwed to optical accessories such as eyepieces or diagonals. Warning: 31.8mm filters do not work with 50.8mm diameter accessories and vice versa (unless there are special adapters). When you choose the version of your filter, be careful to choose the diameter compatible with your equipment.