Start by finding the Great Square of Pegasus, which is rises in the eastern sky during the early fall evenings, is high overhead later in the fall, and sinks in the western sky during early winter. To be sure you know how the square is oriented in the sky, look for the two stars outside the northwest corner of the square (circled in the chart below) that form a small triangle with Scheat.
The constellation Andromeda stretches to the northeast from the Great Square, starting at the second-magnitude star Alpheratz. Using the naked eye, follow the stars of Andromeda east to Almach, magnitude 2. NGC 891 is 3.5 degrees to the east of Almach. To find the spot, it may help to visualize an isoceles triangle with b Andromeda (magnitude 4.8), as shown in the chart below.
