SkyWatcher Refractor ED Black Diamond BK120 optical tube

SkyWatcher offers a wide range of apochromatic refractor optical tubes, with ED treatment . This treatment ensures the correction of the image aberrations , since it avoids an undesired dispersion of light, achieving a much greater sharpness of the image in its entire field.
These tubes are constructed with an air-spaced two-element lens. The second element of the lens is constructed of high-quality fluorinated glass FPL-53. The lenses in contact with the exterior have an anti-reflective coating, which ensures maximum light transmission, by a factor close to 99.5%. This treatment is called high transmission metal treatment.
The objective lens cell is set up to reject residual light that is not focused. The tube itself is designed with internal baffles to ensure maximum contrast , eliminating unwanted light. The interior of the tube is also finished in matte black to avoid the appearance of internal reflections that may reach the focal plane.

This model is a 120mm diameter refractor, with a focal length of 900mm and a focal ratio of 7.5. The focuser is dual speed, crayford 2 " with built-in finder, 8x50mm.
Characteristics:

• ED refractor optical design
  
• Diameter / Opening 120 mm
  
• 900mm focal length
  
• 240x higher practical power
  
• F / F / 7.5 Ratio
  
• Range Finder 8x50
  
• Diagonal 2 "90 degrees. Diagonal dielectric with 1.25" adapter
  
• Diameter 2 "dual speed focuser, crayford
  
• Eye piece LET 2 "-28
  
• Tube 5.13kg Weight
  
• The dimensions of the tube 10x62cm3
  
• Shipping weight 18 kg
  
• Steller weakest magnitude 13.1
  
• Shipping dimensions 124x33x23cm3