By Chris Deziel | Updated Mar 24, 2022
Perseus is one of the oldest catalogued constellations, first recorded by the Greek astronomer Ptolemy in the second century. It is not only a historical gem but also the birthplace of the annual Perseid meteor shower, a mid‑summer spectacle visible across the Northern Hemisphere. One of its most famous stars, Algol, is a binary system that dims noticeably every 68.75 hours. With its hunter‑like shape, Perseus is easily found by using familiar star patterns as guides, or by consulting a star chart.
Begin by locating the Big Dipper, the most recognizable asterism in the northern sky. Although it is part of Ursa Major (the Great Bear), the Dipper’s distinct “pot” shape is a reliable starting point.
Draw a straight line from the two stars at the front of the Dipper’s pot and extend it northward toward Polaris, the North Star. Continue the line beyond Polaris for roughly two‑thirds of the distance you just measured; you will arrive at Cassiopeia, the W‑shaped constellation that also orbits around Polaris throughout the year.
Identify the third star in Cassiopeia’s “W” that is farthest from Polaris. Draw a line from that star to the adjacent star in the “W” and extend it about three times the spacing between them. This will lead you to Mirfak, the brightest star in Perseus.
Find the Pleiades cluster, another easy-to‑spot asterism, and imagine a line running from the cluster toward Polaris. Perseus lies along this line, so this relationship can help confirm your location.
Obtain a star chart tailored to your latitude and the current season. A chart for the specific month is ideal, but a seasonal chart will also suffice.
Face north and orient the chart so that the top represents north. East will appear on the left and west on the right, with the chart’s center corresponding to the zenith. Remember that a star chart is a mirror image of the sky: hold it above your head to view it as it appears in the heavens. If you prefer a direct view, place the chart on the ground and hold it overhead, or use a mirror to flip the image.
Locate Perseus on the chart and note the direction indicated. Head that way and look for Mirfak, the brightest and most visible star. Once you spot it, the rest of Perseus’s stars—including the flickering Algol—will become easier to identify by translating the chart’s lines onto the sky.
Perseus is the 24th largest constellation and can be seen from latitudes 90°N to 35°S. Use a star chart or familiar constellations to locate it.
