... your option.other super achromatic refractor telescope:5inch,D=127mm,f=635mm,other objective size of achromatic refractor telescope:6inch,D=152mm,f ... =1200mm,5inch,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=127mm,f=952mm.