The Astronomik SII-CCD filter, is designed for CCD imaging of gas and planetary nebulae. Due to the narrow bandpass of the SII line, the filter provides maximal increase in contrast even under poor observing conditions. The 13 nm bandwidth allows us to achieve transmission as high as 97% -a value that is impossible to reach with filters of narrower bandwidth.
With faint supernova remnants and planetary nebulae, the Astronomik SII-CCD filter often makes the difference between detecting the object or not. The filter blocks all unwanted light, especially the Mercury (Hg) and Sodium (Na) emissions from streetlights and the IR region where CCDs are often most sensitive.
The optimal focal ratio for the use of this filter is between 1:3.5 and 1:6. The range of application is from 1:2.8 up to 1:15. Unlike other filters of narrower bandpass, loss of transmission with the Astronomik filters does not emerge until focal ratios of 1:2 or faster are used. You can, therefore, image objects within the whole field of view and not only in the middle. This also makes it possible to use the guiding chip of SBIG cameras that otherwise receive almost no light with filters from other companies.
Togther with our H-Alpha-CCD filter and the new OIII-CCD filter you can now do tricolor-imaging of emmision line objects even from very heavy light polluted places.
Due to the well known high optical quality of the glass substrate, Astronomik SII-CCD filters preserve the pinpoint stars to which you are accustomed from your instruments.
The red lines are the most important lines from artificial light pollution. The green lines are the most prominent emission lines for nebulas. The grey curve is the human eye´s night-sensitivity. The blue line is the transmission curve of the filter.
High transmission of nearly 100% at SII.
FWHM of ca. 13nm.
Total blocking of all unwanted light from light-pollution.
The ideal planetary nebulas and supernova remnants.
Completly resistant against high humidity and scratches.
Highest optical quality on the market.
Please, ask for availability before placing your order. Thank you in advance.