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Great Summer Eclipsing Binary Star

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Great Summer Eclipsing Binary Star

Hello Visual Observers,

I'd like to share with you one of my favorite summer-time eclipsing binary stars. OO Aql is a great star for many reasons. First it is amazingly easy to locate. It is right next to Altair, Alpha Aql. The attached star charts show the 0.8 magnitude star, that's Altair. OO is a W UMa type eclipsing binary (EW) with a magnitude range of 9.2-9.9 visual. It only takes 3 to 4 hours to observe. Make observations every 10 minutes or so. Try to get around 15 observations, the more the better. It is good to get several at maximum light right before eclipse begins, then when eclipse is finished, gets a few extra observations back at maximum light.

The primary and secondary eclipses are about the same magnitude range, so you can observe both of the eclipses at the predicted times. I will give you some predicted times of eclipses for this June and July. Begin about 2 hours before the predicted time, and observe for about 2 hours after the predicted time. The predicted time is for minimum light (mid-eclipse). The predictions are good to +/- 20 minutes of accuracy.

June 2012       Times are in UT           Type of eclipse P=Primary and S=Secondary

June 15             00.30UT                                          S

June 16             00:30                                              S

June 17             01:00                                              S

June 30             03:00                                              P

July 1                 03:30                                              P

July 2                 04:00                                              P

July 3                 04:00                                              P

July 4                 04:30                                              P

July 5                 05:00                                              P

July 6                 05:00                                              P

July 21               04:00                                              S

July 22               04:00                                              S

July 23               04:30                                              S

July 24               05:00                                              S


I have attached a "b" scale chart for observers with newtonian telescopes like Dave's 10 inch Dob or my 14 1/4 inch Newtonian and 10 inch Dob.

I have also attached a Reversed "b" for thoise with refractors using diagonals, or those using schmidt/cas telescopes. Good Observing. Roport them on WebObs just like you would any other star.


Chris Stephan

Robert Clyde Observatory

Sebring, Florida  USA

AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484