As many celestial objects; such as nebulae; radiate at other wavelengths; a considerable increase in contrast can be achieved by this; The background sky appears darker and all at once; faint details become visible
1.25 inch filter thread; each Alstar Ultra High Contrast Filter is individually inspected and proudly inscribed with the percentage of light transmittance of the O III and H beta emission lines
Can be used at both light polluted and dark sky sites; Blocks the light from mercury and sodium vapour lamps
1.25 inch Telescope Eyepiece set: Threaded for standard 1.25 inch astronomy filters telescopes and telescope accessories highly compatible; 8 mm 15 mm 40 mm three kind of pass through apertures
Fully-Multicoated Achromatic Design: Featuring a 4-element Plossl optical design with an approximate 50-degree AFOV, perfect for broad field lunar observations; medium sized star clusters; provide a wide range of cloudy nebulas and deep sky targets