The 2 baader safety coolceramic herschel prism visual is for use with refractor telescopes only this v version is for visual use the baader safety coolceramic herschel prism provides the best white light solar views obtainable with superior resolution and contrast the baader herschel safety wedge solar prism uses precision 2 zeiss wedge prism and incorporates a permanently pre installed nd30 filter in the wedge housing