The Astronomik H-Alpha CCD filter, is designed for CCD imaging of gas and planetary nebulae. Due to the narrow bandpass of the H-Alpha line at 656 nm, the filter provides maximal increase in contrast even under poor observing/imaging conditions. The 13nm 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 H-Alpha 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. SCOPE OF DELIVERY Astronomik H Alpha Filter 1.25"
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