The distance we can see through a telescope depends on several factors, including the type and size of the telescope, the observing conditions, and the nature of the objects being observed. In astronomy, distances are typically measured in terms of light-years or parsecs rather than kilometers. These units represent the distance that light travels in one year or the distance corresponding to the parallax angle of one arcsecond, respectively.
Different telescopes have varying capabilities and are designed for different purposes. For example, a small amateur telescope may allow you to see objects within our solar system, such as the Moon, planets, and some brighter asteroids or comets. These objects are relatively close to us, ranging from a few thousand to several million kilometers away.
Larger telescopes, such as those used by professional astronomers, can observe much more distant objects. They can detect stars and galaxies located millions or billions of light-years away. In some cases, these telescopes can even observe objects from the early stages of the universe shortly after the Big Bang.
To put it in perspective, the most powerful telescopes today, like the Hubble Space Telescope or the upcoming James Webb Space Telescope, can observe objects that are billions of light-years away. This means we are seeing light that has traveled billions of years to reach us.
It is important to note that the actual distance we can observe is limited by various factors, including the age of the universe, the expansion of space, and the sensitivity and capabilities of our telescopes. Technological advancements and the development of more sophisticated telescopes continue to push the boundaries of our observational capabilities, allowing us to explore ever more distant regions of the universe.