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CX Aqr

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SET's picture
Joined: 2010-07-23

Hello Observers,


I was out last night observing eclipses of 4 stars. One is one of my all time favorites, and nicely placed for late summer/autumn. CX Aqr is an Algol type eclipsing binary (EA) with a period of 0.5559862 days. It's magnitude range is 10.6-11.8 visual. I love it for 2 reasons.

1. If you print off a "c" chart from the VSP, you will notice the very bright star on it. This is Eta Aqr. CX is just a very short star hop away, following an easy star pattern.

2. This star starts off somewhat slowly, then turns on the speed. Within a 10 minute period (how often you should make an observation), it can drop .2 to .4 magnitude. When it hits bottom, she comes right back up, but at a quicker speed. I always find the ascending branch of the light curve to be a bit more steep than the descending.

Print off a chart and give this one a try. You can get the predicted times of minima from the AAVSO website. Just do a search for Eclipsing Binary Star Ephemerides for 2013.

Good Observing!

Chris Stephan  SET

Burton, OH

Hi Chris, I was unfamiliar
wel's picture
Joined: 2010-07-26

Hi Chris,

I was unfamiliar with CX Aqr and your message prompted me to look up a lightcurve. See:

The ascending and descending branches are mirror images of each other until the star is very close to its out of eclipse brightness.



A great beginners star!
lmk's picture
Joined: 2010-07-23

Yes, this one is easy to find, right on the equator so good for both N or S observers, has a substantial range for visual, and exhibits rapid change during the eclipse too. Excellent for introducing VSO to people at star parties for example!

I could suggest adding another comp star to cover the relatively wide 103-110 range for better estimation. Good choices might be TYC 5233-1997-1 V=10.80 B-V=+0.59 or TYC 5233-1819-1 V=10.72 B-v=+0.60

Mike LMK

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