Calculating telescope magnification is simple: Divide the telescope’s focal length by the eyepiece focal length, in millimeters.
Calculating Telescope Magnification needs a proper understanding of the different terms used in Telescope calculations. Let’s look at some important terms.
- Scope Aperture-this is the diameter of the lens or mirror
- Scope Focal Ratio (f/number)-Focal length divided by aperture
- Barlow Lens- this is a lens that is placed into the focusing tube to increase the telescope’s focal length
- Focal Reducer- this is a device used to shrink the focal length of the telescope.
Telescope Calculator Results
-
- Focal Length-is the distance from the lens or mirror to the image formed
- Magnification – is the level of enlargement of the image on the telescope . Its focal length divided by the eyepiece’s focal length.
- True Field of View-the circle of the sky that you see when you see through the telescope
- Exit Pupil-this is the size of the circle of light hitting the eye when you look through the eyepiece
Factors that Affect Telescope Magnification
- Seeing conditions: these are mostly weather conditions and light pollution which distorts the image. In such cases reduce the magnification
- Size of the Object- every object is different on a telescope depending on its size, for bigger objects use a lower magnification.
- The focal ratio- The longer the focal length the greater is the magnification and the narrower is the field of vision.
- Telescope resolution-Better resolution power makes images clear
Calculating telescope magnification for a Celestron Scope
Magnification for a Celestron Scope
Magnification= Length of Telescope (mm) divided by Length of Eyepiece (mm)
Magnification = Telescope focal length ÷ Eyepiece focal length
For example, if you have a 1000mm focal length telescope with a 25mm eyepiece, the magnification will be 40x (1000mm ÷ 25 = 40).
Remember :
- Never look through window glass, it affects the focus of the telescope
- Hazy skies, fog, and mist will affect your telescope results
See Also
Albert, the founder of Outdoormoran, is a dedicated outdoor enthusiast with a passion for delivering the most current, accurate, and easy-to-understand information on all different outdoor gear and optics. He shares his expertise with beginners by teaching the technical aspects of outdoor gear and optics through his comprehensive collection of guides.