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  • Optolong H-alpha CCD 12nm 31,8mm narrowband nebula filter Optolong H-alpha CCD 12nm 31,8mm narrowband nebula filter

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Optolong H-alpha CCD 12nm 31,8mm narrowband nebula filter

Product code: OPTHALFA318

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Quick Overview

The H-alpha CCD 12nm filter is designed to let precisely pass only the H-alpha line, one of the most important frequencies emitted by faint objects such as nebulae. Due to the very narrow band, this filter generates a high contrast with the complete removal of light pollution making possible long exposure photography also from suburban places. The H-alpha CCD 12nm filter is suitable for use with monochrome CCD cameras because the color models haven't the necessary sensitivity to work well with these filters.

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Regular Price: €105.00

Special Price €65.00

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4.41% discount onOptolong H-alpha, O-III and S-II CCD 12nm filters set 31,8mm

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Regular Price: €340.00

Special Price €325.00


Many faint objects such as nebulae emit light at particular wavelengths: the most important one is the H-alpha line that corresponds to 656nm. By using our H-alpha CCD 12nm filter is possible to "select" only this wavelength (with a bandwidth of 12nm) removing all other frequencies.


Photographic useThis 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 H-alpha CCD 12nm filter can be used together with O-III CCD 12nm and 12nm SII CCD 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 can also be used with color CCD or DSLR cameras, if the latter are equipped with a special modified filter (in front of the sensor) for astronomical use. With these color cameras the image will be completely red (as the H-alpha line corresponds to a part of the red visible spectrum). 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 usebecause of the very narrow bandwidth, the light that reaches the eye is greatly reduced so this filter is not suitable for visual use.



Optolong H-alpha CCD 12nm 31,8mm narrowband nebula filter


Technical specifications:
It selects only the H-alpha line
It cancel the light pollution, making dark the sky background
Transmittance higher than 90% at 656nm
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.

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