Final answer:
To see a dim star, use a telescope and observe from an area with low light pollution. Astronomers use techniques such as color filters and characteristics like variable brightness to determine a star's luminosity and distance. Planets are often easier to observe in infrared to avoid the overwhelming brightness of their stars.
Step-by-step explanation:
If you want to see a dim star, you should use a telescope as it gathers more light than the human eye, allowing you to see stars that are too faint to be visible without assistance. When observing stars in a place with low light pollution, you'll also have a better chance of seeing dimmer stars. Additionally, to determine a star's true brightness (or luminosity) and distance, astronomers use various techniques such as observing the star's properties and characteristics through different filters, like measuring colors through blue, yellow, and red filters.
Astronomers can also look for other characteristics that may indicate a star's luminosity, such as if it's a variable star. For objects that are not stars, like quasars, observing their spectrum and assessing whether the object has an associated galaxy can help distinguish it. In the case of observing a planet around another star, it would often be easier to see in the infrared, as visible light is generally overwhelmed by the brightness of the star.