The Northern horizon at 10:00 pm AEDST on November 25 showing the location of Algol.
Algol is a classic variable star, but is usually hard to see from the southern hemisphere. This week we have a chance to see Algol dim and brighten under reasonable circumstances. Starting around 11:30 on November 25 Algol will begin to dim, being at its dimmest on the 26th at at 00:30 am AEDST.
It's best to start watching from about 9:30-10 pm AEDST on the 25th, when Algol will still be bright, and over the next few hours you can watch it dim dramatically.
You can determine how far and fast it dims by comparing how bright Algol is to neighbouring stars.
Algol and its neighbours at 11:30 pm AEDST. The numbers indicate the brightness of the stars in magnitude. Algol is magnitude 2.1.
To estimate Algols magnitude, compare it to a known brighter stars and known dimmer star. If Algol is dimmer than Almack (2.2) and brighter than the 2.9 stars, it must be around 2.3-2.8.
For more on watching Algol dim and estimating its brightness, see the NHAC Algol project.
For future minima, see the Sky&Telescope minima of Algol page, scroll down to the form that will predict when minima occur in your time zone.