Telescope aperture comparison & Focal length

Every telescope can be chosen on the basis of two criteria because one of the main characters that will be taken into account is either aperture or focal length. Aperture in a telescope is the objective length diameter when it is referred to a refracting telescope or the primary mirror when it is referred to reflecting telescope. So, if you switch to greater focal length, it is clearly better to observe remote objects in space such as the Moon, planets, etc. or if you require better observation of DSO (deep space objects) such as galaxies getting a device with greater aperture figures is better.

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