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Special Notice #192: Update on the epsilon Aurigae eclipse

February 3, 2010: Epsilon Aurigae continues to progress through its first eclipse since 1982-84. Visual and photometric observation means place it at around magnitude 3.7-3.8. Totality was likely reached sometime in January, but it will take some time to analyze the data to establish a specific date. Totality is expected to last about 15 months, but the system is not expected to remain quiet during this time. Small amplitude modulations are being detected which are likely not associated with the eclipse itself. However, their exact source is still debated. The amplitude of these modulations are at the limit of the average observer's ability to detect visually. Therefore this may make a nice, challenging system to test your eyes. Right now, epsilon Aurigae is well placed for observing high in the sky right after dusk.

In addition to these modulations, a mid-eclipse brightening of a few tenths of a magnitude have been reported in past eclipses. If confirmed, it would contribute significantly to our understanding of the structure of the eclipsing disk of material. The problem is this will happen next summer when epsilon Aurigae is near solar conjunction. So observations very early in the morning later this season will be very important. It may be a good idea to begin practicing twilight observations right now.

A naked-eye, visual chart for observing epsilon Aurigae can be downloaded at:

Observers interested in DSLR or photoelectric photometers may want to use this project as an entry point. A team of observers is working on a series of tutorials on the Citizen Sky web site. More information is available at the following URL:

General information regarding the epsilon Aurigae campaign and a series of online discussion forums can be found at the Citizen Sky web site:

A nice illustration of the system has been prepared by Citizen Sky participant Nico Camargo:  [broken link]

This AAVSO Special Notice was prepared by Aaron Price.


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