Bob Moler's Ephemeris Blog

Ephemeris for Halloween, Wednesday, October 31st.  The sun will rise at 8:19.  It’ll be up for 10 hours and 12 minutes, setting at 6:32.   The moon, 2 days past full, will rise at 7:37 this evening.

Not all the ghosts and goblins out tonight will be children.  One will be out every night, because it’s a star.  Its name is Algol, from the Arabic for Ghoul Star or Demon Star.  The Chinese had a name for it that meant a mausoleum or more ominously ‘piled up corpses’.  It’s the second brightest star in the constellation Perseus the hero, rising in the northeast this evening.  The star is located where artists have drawn the severed head of Medusa, whom he had slain.  Medusa was so ugly that she turned all who gazed upon her to stone.  Algol is her still glittering eye.  Astronomers finally found out what was wrong with Algol.  It does a slow 6 hour wink every two days 21 hours, because it is two very close stars that eclipse each other in that period.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Addendum

The constellation Perseus in the northeast at 9 p.m. on October 31, 2012. Created using Stellarium.

Perseus and the head of Medusa from the 1690 Uranographia by Johannes Hevelius. Image found with the article on Algol in Wikipedia.

Note that this is a mirror image.  The star charts in the 17th century were based on celestial globes, which represented the constellations as seen from the outside of the celestial sphere instead of from the inside.  I reversed the image to match Perseus as we see him.