A newly refined Precision Interference Filter for Astronomers that selectively transmits the Hydrogen and Oxygen emission of Galaxies while elliminating the background polluting light. Produced exclusively for EBay customers as an economical yet improved Deep Sky Filter. This filter has had significant development to produce excellent transmission of the Oxygen lines at 496.9 nm, 500.4 nm, as well as the 486 Hydrogen, while attenuating most of the background light from other sources. The filter has an exceptionally rectangular passband, and very good attenuation of the remainder of the visible spectrum. This is a relatively broad pass band nebula filter.
The broad-band "Light Pollution Reduction" (LPR) filters are designed to improve the visibility of a variety of Deep-Sky objects by blocking out the common Mercury vapor, Sodium, and some other emission lines from man-made or natural sources which contribute to light pollution, while letting through a broad range of other more useful wavelengths. Since the eye is mainly a "contrast detector", this selective screening out of some of the background skyglow increases the contrast and helps Deep-sky objects stand out more noticably. While these filters do not eliminate the effects of light pollution or make the objects brighter, in many cases, these filters can improve the visibility of some deep-sky objects to at least some degree.
The filter is mounted in a threaded eye piece adapter commonly refered to as 1.25". (Actually a 28 mm standard configeration.)and has an glass filter dimension of 26 mm.
Specifications follow: Central Wavelength 494 nominal, To pass 480 to 520 nm, Typical transmission >90%, Blocking OD 3 typical of interfering light. Filter supplied with actual spectral data.