... super achromatic optical system,better optical performance for 6 achromatic refractor telescope - doublet achromatic objective lenses,additionalfocus reducer for super ... ,D=127mm,f=820mm,4inch,D=102mm,f=1000mm,4inch,D=102mm,f=660mm.other ED APO refractor telescope:3.15inch,D=80mm,f ... =480mm,4inch,D=102mm,f=700mm,5inch,D ...