It is known as urban astronomy, astronomy in public spaces, sidewalk astronomy[1]​ or street astronomy,[2]​[3]​ to the activity of installing a telescope in an urban location, generally non-profit, for entertainment or educational purposes.

Examples of people setting up telescopes on city streets so that the public could observe the sky date back to the century and perhaps even earlier.[4]​[5][6]​[7]​ Sidewalk astronomers and their telescopes were a relatively common presence in many large cities.[8]​ There are many well-known early examples, such as Frank Manning in New Orleans (circa 1930), or "Mr. Grosser" in Los Angeles (in the 1870s), who in addition to a telescope, installed a microscope equipped with light.[9] Some of these street astronomers charged for showing astronomical objects through their telescopes, but many others let passersby view them freely.[6][10]​.

A well-known example is the case of the American astronomer John Brashear (1840-1920). When he was nine years old, his grandfather took him to look through the traveling telescope that 'Squire' Joseph P. Wampler had set up in the small town of Brownsville. That fleeting vision of the moon and the planet Saturn "Saturn (planet)") impressed Brashear to the point of conditioning his professional vocation for the rest of his life.

In more recent times, street astronomy has become almost exclusively linked to people or groups that altruistically offer citizens in general the possibility of observing the night sky through their telescopes, as a free public educational service.[11]​.

Because the streets of most cities have light pollution problems, urban astronomers often coordinate their activities around times when the most prominent celestial objects, such as the moon, planets, and the brightest stars, can be observed. During the day, filters are used on the telescope to be able to contemplate the sun. The telescopes used are sometimes much larger than the commonly marketed models.[1][11]​.

With the proliferation of amateur astronomical groups, these street activities have become associated with the public dissemination of astronomy, making contemplation of the sky available to anyone who wishes to look through a telescope. These events usually involve more or less large groups of amateur astronomers equipped with medium and small telescopes. Organizations such as the San Francisco Sidewalk Astronomers, founded by astronomer John Dobson, revolve around the idea that to educate people about the universe in which they live, they need to view it through a telescope.[12][13][14][15] Dobson even promoted the design of a large, low-cost reflecting telescope for amateurs, which he called ", better known as the Dobson telescope.[16]​.