| All Astronomik CCD filters are parafocal, no refocusing is necessary after changing filters. Astronomik CCD Filter Quality Characteristics: Superior Substrate:
Astronomik filters consist of a precision polished substrate on which the actual filter, in the form of very thin dichroic layers, is applied. These high quality measures will in no way reduce the performance of your optical train. Contrary to common experience with other manufacturers' filters, with Astronomik filters stars remain fine needle points of light! Coating:
Astronomik filters consist of up to 130 layers deposited on top of the completely transparent carrier glass. These layers comprise both the actual filter and an antireflective coating. Parfocal Filters:
All Astronomik CCD Filters are parafocal. When changing filters, the focal point will not change; you will not have to refocus your camera. This is due to the high tolerance and very low thickness of the substrate and coating. Durability:
Astronomik filters are completely scratch resistant, and not sensitive to moisture, dew, or high humidity (touching a dewedup filter will, of course, not destroy it... if it is made by Astronomik!). With other filters, after a few years, you quickly notice their filters degrade and are not at their full, new capability. Not so with Astronomik filters which maintain their "brand new" transmission specifications. And, because of Astronomik's extraordinarily resistant coating technology, our filters come with a 10year warranty. Comparing Astronomik CCD Photographic Filters to our Visual Filters:
Unlike Astronomik Visual Filters which do not require IR blocking, our Astronomik CCD Photographic Filters do include IR blocking filter layers to prevent any problems from Infrared Radiation (IR) when using CCD and chemical photographic devices. | 
