The number of constellations you can identify from your backyard depends on a few factors, including your geographical location, the time of year, and the level of light pollution in your area.
Geographical Location: The constellations visible to you depend on whether you are in the Northern or Southern Hemisphere. For example, constellations like Ursa Major and Cassiopeia are staples of the Northern Hemisphere, while the Southern Cross and Centaurus are prominent in the Southern skies.
Time of Year: As the Earth orbits the Sun, different parts of the sky become visible at different times of the year. For example, Orion is a winter constellation in the Northern Hemisphere but can be seen in the summer skies in the Southern Hemisphere.
Light Pollution: The level of artificial light can significantly affect what you can see. In urban areas with high light pollution, only the brightest constellations and celestial objects might be visible, such as Orion, Leo, or the Big Dipper asterism within Ursa Major. In contrast, rural or dark-sky areas might allow you to identify dozens more, including fainter constellations like Cancer and Pisces.
Horizon Obstructions: Trees, buildings, and mountains can obstruct your view of the horizon and limit visibility to certain constellations, especially those that are lower in the sky.
On a clear night with minimal light pollution, typically 30 to 40 constellations can be visible at a time, though identifying them requires some familiarity with star patterns. Using a star map or an astronomy app can help locate and identify these constellations accurately.