3 ms·

Yep, the trick, is to look at the brightness relative to a non-variable, or less variable star. Also, note that the observations of Algol from the 1600s were j

Yep, the trick, is to look at the brightness relative to a non-variable, or less variable star. Also, note that the observations of Algol from the 1600s were just the first documentation of the star – observations of variability didn't happen until the 1700s – I'm not smart, I just checked Wikipedia as I was reading up around this topic :)

teraflop 11y ago
You might want to read that Wikipedia article more closely; it mentions that Algol was written about by Ptolemy in the 2nd century.
- codezero 11y ago
  You're totally right, and the variability was in the 1600s – foot in mouth! Thanks for pointing this out to me.