Astronomik SII 6nm Narrowband CCD Filter

£182.00✓ 2 year warranty

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About this product

Model: ak_sii-ccd_6nm_125
Part Number: 10216625

The Astronomik SII Filter is suitable for imaging of SII-regions from observation sites with light pollution and from dark sites as well. The contrast between an object glowing at 672nm and the background is increased enormous!

Due to the combination of the narrow bandwidth of 6nm and the high transmission of typically 96% the filter gives you an contrast boost, as all unwanted light from other wavelengths than 656nm is blocked form UV up to the IR. This results in an very dark background compared with any filters with a higher bandwidth

The FWHM of 6nm is matched to give you optimal performance with CCD and CMOS sensors with a very low dark current! The 6nm filter is the best choice if you are observing from a heavily light polluted site or if you are imaging faint objects in star-crowded regions of the milky-way.

Due to the new MFR coating technique you may use one single filter on all instruments up to f/3 without a significant reduction in performance.

FEATURES

Guaranteed Transmission of more than 90% at the SII Line (672 nm)
Typical Transmission of 96% at the SII Line (672 nm)
Full-Width-Half Maximum (FWHM): 6nm
Perfect blocking of unwanted light from UV up to the IR
MFR Coating technique: Usable with all optics up to f/3
Optically polished substrate, striae-free and free of residual stresses
Not sensitive to high humidity or ageing effects
Scratch-resistance!
Excellent quality substrate, diffraction limited - the optical performance of your telescope will not be reduced
Parfocal with other Astronomik filters
1mm Glass Thickness
Supplied in a high-quality, long lasting, filter box

Imaging with Narrowband Filters

If you have to observe from light polluted sites (like most of us...), imaging with narrowband filters is the best way to take great images, as all kind of light pollution can be blocked very effective! Normally an H-alpha filter should be your first step into this amazing field of astrophotography! With an Narrowband H-alpha filter you will be able to take deep and contrasty images even with very heavy light pollution or with the full moon high up in the sky!

If you look at other astro-photos, an H-alpha is the best choice for all nebulas glowing red! An OIII filters expands your imaging possibilities, as you are able to image all greenish/blueish structures. Planetary nebulas and star forming regions are great targets! The SII filters completes your HSO-set of filters. With these three filters you are able to process your images like the ones from the Hubble space telescope!

Operation of the filter

The filter blocks all unwanted light from artificial light-pollution, natural airglow and moonlight. Especially light from High- and Low-Pressure Sodium and mercury lights and all lines of natural airglow are 100% blocked. The filter increases the contrast between the sky-background and objects glowing at the SII line at 672nm.

Tips and Hints for more applications

Using the SII filter together with OIII-CCD and OIII-CCD filters you make produce false-colour emission line images (HSO) in the same way as the Hubble-Space telescope. This is possible even from heavily light polluted sites!

Alternatives

The lower priced 12nm filters are the right choice for you, if you own a typical DSLR or a CCD camera with a high dark current! The 12nm filters should be the fist choice for cameras with an integrated guiding sensor, as you will have about twice as much stars compared to the 6nm filter.

Transmission Chart

The horizontal axis is the Wavelength in Nanometers (nm). 400nm is deep blue, at 520nm the human eye senses green and at 600nm red. At 656nm is the famous "H-Alpha" emission line of hydrogen.
The transmission in % is plotted on the vertical axis.
The blue line shows the transmission of the filter.
The most important emission lines from nebulas are shown in orange. The most important lines are from ionised Hydrogen (H-alpha and H-beta) and double ionised oxygen (OIII).