How far can I see with a telescope?
February 13, 2005
The farthest you can see in the sky with your telescope will depend on its ability to gather light and where you observe.
The most distant objects visible with amateur-sized telescopes are faint galaxies and the brightest quasars. They will be brighter and easier to see in a scope that gathers more light and has a greater magnitude limit (two topics discussed elsewhere in the Knowledgebase). Here bigger is better and a larger aperture scope will see more remote objects.
Location is also important. Even with a big scope, you’ll see fainter, deeper and farther out into the universe from an isolated dark-sky site than from the heart of a megalopolis.
For example: quasars are all very faint as seen from the earth. The brightest one is 3C 273 in Virgo. It is magnitude 12.9. A good 4 in scope is capable of seeing it in dark-sky conditions. You’ll need a larger scope to see it at all from a city.
This quasar is an active galactic nucleus that is located about 2.6 billion light-years from the earth. For more information on 3C 273, go to the SEDS web page.