Each Alstar 1.25 inch O III Filter is individually inspected and proudly inscribed with the percentage of light transmittance of the two O III emission lines
Not only useful at light polluted sites; the contrast is also increased at dark sky sites; can be used with all 1.25 inch eyepieces; Filter made from high grade glass with dichroic interference and antireflection coatings
Completely blocks virtually all other visible wavelengths of light so views of nebulas are optimized; Increases contrast through selective filtration Anti reflection coated to prevent glaring and ghosting
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
Wide Field of View : 1.25 Inch 4mm 10 mm 20 mm Plossl eyepiece offers a wide field of view and long eye relief ideal for high-precision astronomical observations