Normally, Algol is a magnitude 2.1 star, plenty bright
enough to be seen even in urban skies. But about every 3 days, one of the stars
eclipses the other, causing it's magnitude to drop to about 3.4.
Like any scientific experiment, one cannot let preconceived notions spoil the
observations. Although we know that Algol varies from 2.1 to 3.4, there may be
surprises! In 2000, naked eye observers noticed a star in Scorpius, Delta Scorpii, that
had suddenly increased in brightness, where no variability was known to exist before.
Sky & Telescope Articles:
If you can find the Pleiades, you can find Algol. During early evenings in February, the Pleiades will be high
in the sky overhead, and towards the west as evening progresses. Algol is just north of the Pleiades,
in the constellation Perseus. So stand looking west, look high overhead to see the Pleiades, then look
towards the right (north), to see Perseus. Use the finder charts:
to see what the star field looks like. Once you identify Algol, compare it to the other
stars shown in the charts. The numbers on the chart indicate magnitude, with the decimal
point omitted.