Astronomical telescope refractive 70MM dual separation objective, with a diameter of 72mm and a focal length of 300400500700900mm, blue coating, is a good choice for DIY medium caliber astronomical telescopesAstronomical telescope objective D=70mm F=300mm blue filmD-type movement: 72mmFocal length F: 300 millimetersClothing: Single piece blue filmIntegrated image quality: 1/4-1/8Diameter tolerance:+0/-0.12 millimetersCenter thickness tolerance: 0.2 millimetersFocal length tolerance: 0.1%Completion: 60/40Strange: 1 'Comment: Two sets of refractive double separation objective lenses;Used for astronomical telescope objectives, framing lenses, and collimating objectivesAstronomical telescope objective D=70mm F=360mm blue filmD-type movement: 72mmFocal length F: 360 millimetersClothing: Single piece blue filmIntegrated image quality: 1/4-1/8Diameter tolerance:+0/-0.12 millimetersCenter thickness tolerance: 0.2 millimetersFocal length tolerance: 0.1%Completion: 60/40Strange: 1 'Comment: Two sets of refractive double separation objective lenses;Used for astronomical telescope objectives, framing lenses, and collimating objectivesAstronomical telescope objective D=70mm F=400mm blue filmD-type movement: 72mmFocal length F: 400 millimetersClothing: Single piece blue filmIntegrated image quality: 1/4-1/8Diameter tolerance:+0/-0.12 millimetersCenter thickness tolerance: 0.2 millimetersFocal length tolerance: 0.1%Completion: 60/40Strange: 1 'Comment: Two sets of refractive double separation objective lenses;Used for astronomical telescope objectives, framing lenses, and collimating objectivesAstronomical telescope objective D=70mm F=500mm blue filmD-type movement: 72mmFocal length F: 500 millimetersClothing: Single piece blue filmIntegrated image quality: 1/4-1/8