Light gathering power is one measure of the performance of a telescope.
It is roughly proportional to the square of the aperture size. A telescope with an aperture twice the diameter collects approximately 4 times as much light.
Light Gathering Power
The ability of a telescope to collect light. Proportional to the are of the telescope objective lens or mirror
Light-Year ...
The light gathering power of a telescope is proportional to its diameter squared. The Keck telescope has a diameter that is 4 times bigger, hence its light gathering power is 42=16 times as great.
The light gathering power of a spotting scope is determined by the width of the objective lens, typically between 55 and 80 mm. All else being equal, the larger the objective, the more heavy and expensive the telescope.
Gemini has 10 times the light gathering power of the Hubble Space Telescope, and 4 times the power of the William Herschel Telescope, allowing astronomers to study much fainter (and hence, more distant) galaxies.
its light gathering power should be high which can be achieved by using an objective lens of large diameter in case of a refractor. A reflecting telescope too requires this.
This is an extremely important attribute, as virtually all X-ray sources are weak, and maximizing the light gathering power of a mirror system is critical.
aperture
The size of the main mirror or lens of a telescope. The aperture of a telescope is a measure of its light gathering power.
3 may make it a bit challenging to find with binoculars, but it is an easy target for the telescope. As is the rule with most galaxies, bigger is definitely better. The light gathering power of a large telescope will reveal much more detail in the ...
 See also: Light, Telescope, Astronomy, Earth, Star
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