A short telescope glossary



If you are looking for a short telescope glossary, here are the most relevant terms to keep in mind. There are many new words to learn about, but once you get more acquainted with them, things will become easier to understand.

Aperture – this is the most important factor to learn about in a telescope. It represents the diameter of the lens, and the larger this number is, the more light will be filtered through the device. That means that the image of the stars you need to gaze upon will be much clearer, due to the significant amount of light gathered.

To give you an idea about the importance of aperture in a telescope, you should know that doubling the aperture value, leads to multiplying the light gathering capacity of a telescope four times.

Altazimuth mount – the mount on which the telescope should be placed must have two axes. One should move up and down – which counts for moving on altitude, while the other should move side to side – which counts for azimuth moving capability. You may notice similarities between this type of mount and a tripod used for photography.

Apparent magnitude – this value measures star brightness as it appears to the naked eye. You will notice that a lower apparent magnitude stands for a brighter star.

Coated optics – the lens must have a certain type of coating, to enhance contrast and improve light transmission. Coated optics have a layer of magnesium fluoride applied to the lens.

Dobsonian – this is the name given to an altazimuth mounted model that is supported by a rocker box base. Its name is derived from the person who created the design, an amateur astronomer by the name of John Dobson.

Focal length – while this term is not as important as aperture, the focal length of your telescope plays a major role in your stargazing capabilities. The term is used to describe the distance between the lens and the focal point.

Focal length is closely related to magnification. The higher the first, the better the latter. Aperture, however, limits the value of the focal length.

Focal ratio – this term is used to describe the optical design of the device you are using. It is calculated as the ratio between the focal length and the aperture. You must bear in mind that this specification does not play any role in image quality.

However, it is important when pictures must be taken. A model with a smaller focal ratio is usually faster than one with a larger focal ratio. For telescopes, this may not be essential, unless you want to make a difference between so-called faster and slower telescopes.

Resolution – this term stands for the capacity of a telescope to show a more detailed picture of the celestial body you examine through the device.