Spark and Perl go looking
Nothing is happening.
Give it an hour.
…Still nothing.
Give it another hour.
It went dim!
Perl, you have broken it!
There are two stars there.
The dim one has slid in front of the bright one.
It will do it again in a couple of days, and it has never once been late.
The star shrank. I watched it happen.
Nothing shrank, Spark.
…The dim one walked in front of the bright one.
It is a shadow, not a shrinking.
Every two days and a bit.
Yes.
Compare it with the star beside it after supper, then again before you sleep.
You can see this from almost anywhere — but not the very far south.
Where to find Algol, and when
Where the Earth is clear, it climbs high in the sky. The darker it gets, the lower it stays. Where it is black, it never comes up. No shading at all: it does not matter where you live.
What do I need to see Algol?
You can see it with just your eyes.
You can actually watch it happen.
Binoculars with 10× magnification show it, if you rest them on a fence or a wall.
A 150 mm telescope does not make it better — this is about comparing brightness, not about magnification.
Space
Eyes, binoculars, or telescope?
Read on
Go and look