THE LARGER THE APERTURE OF A TELESCOPE, THE IMAGE WILL BE BRIGHTER AND MORE DETAILED.
Aperture is all about gathering light. The human eye can only gather as much light as can squeeze through
the pupil of your eye. Not much. So the real purpose of a telescope is not magnification, but gathering more
light. The bigger the aperture, the brighter the image. You won’t enjoy looking at a dim object, no matter
how big you make it. That’s why any experienced astronomer will tell you aperture is everything.
As a general rule, an 8-inch telescope has four times the light gathering power of a 4-inch telescope. The
images below were created to simulate the view through telescopes of different apertures
at the same magnification. Examine them and it’s easy to see why bigger is better.
The main caveat to the “bigger is better” rule is portability. For example, a 10" telescope will give brighter
and more detailed images than an 8", but becomes increasingly more
difficult to transport to your favorite dark sky location (of course this is not an issue if you plan on a home
observatory or roll-off shed).
But the best scope for you is the one you will actually use. Most amateurs consider an 8" scope the perfect
compromise between brightness and portability.
Despite this truth, no photograph can compare with the experience of standing under a clear sky and looking at a nebula or galaxy 1,500 light years away with your own eyes. It’s sort of like comparing a photo of a rainforest to actually being there.
Depending on viewing conditions (e.g. the steadiness of the atmosphere and the darkness of your location) a large scope will turn distant galaxies, star clusters, nebulas and planets into truly magnificent sights you will never forget.
Remember
: Never look at the Sun with an unfiltered optical device or your naked eye.
It will result in blindness.