## Telescope Diffraction Limit: Explanation & Calculation

The diffraction limit is the highest angular resolution a telescope is able to achieve. This limit refers to the theoretical maximum if nothing besides the size of a telescope’s light-collecting area affects the quality of the images. This limit is a direct consequence of the nature of light waves. When light waves encounter an obstacle […]

## Telescope Field of View (FOV) Calculation

The field of view (FOV) in a telescope defines the extent of the observable universe that is visible through the eyepiece at any given moment. Knowing the FOV allows astronomers to determine the ideal eyepiece for a specific observation. There are two distinct types of FOV: the apparent field of view (AFOV) and the true […]

## Telescope Light Gathering Power: Calculation

The light gathering power (LGP) refers to the telescope’s ability to collect light. Knowing the LGP of a telescope is important because the more light a telescope can gather, the better its ability to observe faint objects in the night sky. The LGP is measured in terms of the area of the telescope’s aperture, usually […]

## Telescope Resolution (Resolving Power) Calculation

Resolving power, also referred to as “resolution” or “angular resolution”, is a measure of a telescope’s ability to differentiate between two closely spaced objects. Knowing the resolving power of a telescope allows astronomers to understand the capabilities of its optics. The resolving power is defined by a combination of factors, including the diameter of the […]

## Telescope Magnification (Magnifying Power)

Telescope magnification, often referred to as “power” or “telescope zoom,” defines how much a telescope can enlarge the appearance of distant objects. Magnification is the factor by which a telescope amplifies the size of an object compared to its size as seen with the naked eye.  A telescope’s magnifying power is determined by dividing the […]

## Telescope Focal Ratio: Explanation (F Ratio & F-Number)

Focal ratio, also known as the “f-number,” “f-ratio,” or “aperture ratio,” defines the relationship between the focal length of a telescope and the diameter of its primary optic. The focal ratio is calculated by dividing the telescope’s focal length by the diameter of the aperture.  Knowing the focal ratio is crucial as it serves as […]

## Telescope Focal Length: Explanation

Focal length is the distance between the objective lens or mirror of a telescope and the point where incoming light converges to form an image. Knowing the focal length allows observers to comprehend key aspects of a telescope’s performance. To calculate the focal length of a telescope or lens, measure the distance from the lens […]

## What Is A Telescope Aperture? Explanation and Size Comparison

Telescope aperture is the size of the primary optical element. Knowing the aperture of a telescope allows observers to understand the light-gathering ability and resolution. For amateur telescopes, apertures range from 50mm to 130mm in diameter. Knowing the aperture diameter size also allows telescope users to understand the focal ratio and focal length. These values […]

## How Does a Telescope Work? Functions of Optical System

A telescope works by collecting and focusing light from distant objects. The objective gathers and bends light. The objective is either a lens, in refractor telescopes, or a mirror in reflector telescopes. Light is then focused into the eyepiece, which magnifies the image, enabling detailed observation of distant celestial bodies. Atmospheric conditions significantly impact the […]