Barlow lens
Magnification of telescopes is calculated by dividing the objective focal length with the eyepiece focal length. To change the magnification, a different eyepiece must be… Read More »Barlow lens
focal length
Aperture, focal length and focal ratio
Aperture One of the essential features of a telescope is its aperture. Depending on the type of telescope, the aperture can be either a lens… Read More »Aperture, focal length and focal ratio
Lowest and highest useful magnification
Magnification is the ability of a telescope to magnify an object. A lot of observers, not only beginners, don't understand why higher magnification often doesn't… Read More »Lowest and highest useful magnification