Forums / The Science / Visual Observing / Observing an eclipse of Beta Persei, or Algol
Observing an eclipse of Beta Persei, or Algol
I had the fun experience of observing an entire eclipse of the famous eclipsing binary star Beta Persei, better known as Algol. I happened to be attending the Chiefland Star Party in north Florida and we were blessed with 3 clear nights in a row. On the night of November 13-14, 2009 the eclipse was predicted to take place around 8:30PM EST, or 01:30UT. The predictions are to about +/- 20 minute accuracy. Just as the sky got dark enough to observe, I started on the eclipse.
First I made sure I identified the correct star (I have observed eclipses of Algol many times). I use an AAVSO chart, probably an older version than what the Variable Star Plotter VSP on the AAVSO web site would generate. I do not use the chart in the "10 Star Tutorial", just because I am so used to my old one, I am more comfortable with it. My comparison stars are 2.1, 2.9, and 3.8. Algol ranges from roughly 2.1 to 3.3 during an eclipse, which takes about 5 hours to observe the entire eclipse. Right on time I noticed the star beginning to dim. I make observations naked eye, about every 10-15 minutes. For this particular eclipse I made 29 observations of the star. I began at 6:25PM EST and observed until 11:55PM.
Aaron is going to attach a copy of the observations and the light curve, so that you can see exactly what took place. It looks like mid-eclipse was somewhere around 9:00PM. So, the eclipse happened very close to the predictions.
I would like to encourage people to go out and observe an eclipse of Algol this fall/winter. I believe Aaron has put the eclipse predictions on the Events calendar. Just set aside 4-5 hours to observe. Be comfortable, make some hot cocoa, and enjoy this famous star as it does it's thing. Please submit your observations through the Citizen Sky web site.
Chris Stephan
Robert Clyde Observatory
Sebring, Florida USA
Algol is a GREAT starting point for new observers. Like eps aur, it is very bright and easy to see - even from the city. And since the eclipse is so short you can really see what a variable star cycle looks like in one evening. I know many a person who first got bitten by the variable star bug after watching Algol. It has the nickname of the "Demon Star" because its mysterious eclipses were frightening to many cultures. It's another example of mythological archetypes, where one object has the same meaning in many different cultures. Here is a light curve of Chris' observations from last Friday. Notice the flat bottom, which is indicative of most eclipsing objects. The flat bottom of epsilon Aurigae will be much bigger by proportion than this light curve. Can anyone suggest why that may be?
(Try using our new light curve tool to make your own plots of Chris' data.) There are many well-timed eclipses of Algol coming up in December. I recommend taking advantage and trying to get a few observations. We'll make certificates for anyone who observes at least half of an eclipse. Click here to view the December eclipse predictions via our Event Calendar.