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Home / Products / Astronomy Mirror / D51F219 Diameter 51mm Refractive Green F
D51F219 Diameter 51mm Refractive Green Film Telescope Achromatic Objective

D51F219 Diameter 51mm Refractive Green Film Telescope Achromatic Objective

D51F219 is a 51mm diameter refractive green film achromatic doublet objective lens with a 219mm focal length, designed for use in refracting astronomical telescopes and optical collimators. The lens is made from K9 glass with a green anti-reflective coating to improve light transmission and reduce glare. It is supplied as a single unit and is suitable for precision optical systems requiring high clarity and minimal chromatic aberration.

  • 51mm diameter aperture provides high light-gathering capability for astronomical observations
  • 219mm focal length enables long focal ratio systems suitable for detailed planetary and lunar imaging
  • Green film coating reduces surface reflections and improves contrast in bright and low-light conditions
  • Achromatic doublet design minimizes chromatic aberration across visible spectrum
  • K9 glass material ensures consistent optical performance and durability
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Technical features

  • Focal length: 219 mm
  • Diameter: 51 mm
  • Material: K9 glass
  • Coating: Green film anti-reflective coating
  • Type: Achromatic doublet lens
  • Application: Refracting astronomical telescope objective lens or optical collimator
  • Package: 1 piece per unit

Who it is for

  • Amateur and professional astronomers building or maintaining refracting telescopes
  • Optical engineers designing collimators or beam shaping systems
  • Manufacturers of astronomical instruments sourcing replacement or upgrade components
  • Educational institutions setting up lab-based optics experiments

Specifications

Focal Length219 mm
Diameter51 mm
MaterialK9
CoatingGreen film
TypeAchromatic Doublet Lens
ApplicationRefracting astronomical telescope objective lens / optical collimator
Package1 PC

Use guide

  • Use only with compatible telescope tube and focuser systems that support 51mm diameter lenses
  • Align the lens carefully with the optical axis during assembly to prevent vignetting or distortion
  • Clean the lens surface with lens tissue and appropriate cleaning solution to preserve coating integrity
  • Avoid touching the optical surface; use lens caps when not in use

FAQ

What is the focal length and diameter of the D51F219 lens?
Focal length is 219 mm, diameter is 51 mm.
What material is used in the lens construction?
The lens is made from K9 glass with a green film anti-reflective coating.
Is the lens coated to reduce reflections?
Yes, it has a green film anti-reflective coating to improve light transmission and reduce glare.
Can this lens be used in a refracting telescope?
Yes, it is specifically designed as an objective lens for refracting astronomical telescopes.
How many lenses are included in one package?
One piece per package.

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