Telescope Magnification
The angular magnification of an astronomical (refracting) telescope. The negative sign indicates an inverted image.
Variables
Derivation
Derived from the ratio of the angle subtended by the image to the angle subtended by the distant object. The objective forms an image at its focal point, which coincides with the focal point of the eyepiece.
Your notes
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- fo = 2 m (Focal length of objective)
- fe = 3 m (Focal length of eyepiece)
Result: M = -0.66666667
Where this formula is listed
- Optics formulas, under Optical Instruments, alongside Numerical Aperture, F-Number (f-stop) and Depth of Field.
- In the optics list it comes after Microscope Magnification and before Numerical Aperture.
- Optics formula sheet, one of 34 formulas printed with symbol keys and SI units.
- The full formula index, grouped by category and topic.
Common questions
What is the Telescope Magnification formula?
Telescope Magnification is written M = −f_o/f_e. The angular magnification of an astronomical (refracting) telescope. The negative sign indicates an inverted image. It belongs to Optics, under Optical Instruments.
What are the units in M = −f_o/f_e?
In SI units, M is angular magnification (dimensionless); f_o is focal length of objective, measured in m; f_e is focal length of eyepiece, measured in m.
How is the Telescope Magnification formula derived?
Derived from the ratio of the angle subtended by the image to the angle subtended by the distant object. The objective forms an image at its focal point, which coincides with the focal point of the eyepiece. The result is M = −f_o/f_e.