Visual Observations of Eclipsing Binaries

American Association of Variable Star Observers (AAVSO)
Mon, 02/03/2014 - 18:42

The Variable Star League of Japan (VSOLJ) has just issued their Variable Star Bulletin no. 56 (Visual and CCD minima of eclipsing binaries during 2013). One of the AAVSO's long time visual observing advocates, Chris Stephan (SET) features quite prominently in the results. 

He is observing some EBs that otherwise would not have any results to publish, and his visual O-C results match up pretty well with the CCD and DSLR observers on the stars they share in common.

Good for you, Chris!

Variable Star Observers League in Japan (VSOLJ)
Visual observer

Thank you Chris for introducing the latest issue of VSOLJ bulletin.

After AVVSO decided that they don’t publish visual observations of minimum timings of EBs, Chris Stephan (SET) has reported his results to Kazuo Nagai, our curator of EBs observing.

Because, they are already friend before SET start to send his results to VSOLJ and VSOLJ bulletin still accepte visual observing of EBs.
But, in 2013 results, SET is only visual observer even in our report.

We will continue to accept and publish visual observations of minimum timings of EBs as long as visual observers exist.

Seiichiro Kiyota
VSOLJ and also AAVSO member

PS. Takumi Tanaka is only young person in 2013 report. He is a junior high school student. Others are old men. We need to encourage young observers to observe EBs.

thank you


Thank you for kind words on this post and forum. I cannot understand why more people, young and old, men and women, are not observing eclipsing binaries visually. I think that there is a faulty message that has been put to amateur astronomers out there. Eclipsing binary star observing is NOT just for ccd observers, but for visual also. I will continually observe them.

In fact, I just came in from making 45 estimates of 3 eclipsing binaries: SV Cam, ER Ori, and EQ Tau.


Chris Stephan   SET

Robert Clyde Observatory

Wooster, Ohio

British Astronomical Association, Variable Star Section (BAA-VSS)
Visual observations of eclipsing binaries.


I agree, visual observations are both fun and useful.  After spending a long time getting to grips with ccd photometry I am now rediscovering the benefits of visual work, and feel that they complement each other. 

My ccd telescope is a 2 inch refractor, which has a limited range without using ridiculously long exposures.  I can go deeper visually with my 14 inch Dobsonian, and have recently observed BV Tau (results to follow).

Speaking as someone verging on being an 'old man' (I'm 60 years young), I also feel that we need to encourage younger people to take up variable star observing, or astronomy in general, for that matter.  My own local societies are very top heavy when it comes to age and gender.

David Conner (CDSA).

Melton Mowbray, England.

Neglected EB stars

  You can count me as one of those visual observers who has shied away from eclipsing binary stars, but these posts are encouraging. I may take it up again soon. I've spent some time using VSX in the last few months, and I've noticed that there are a lot of EB stars with few or even no estimates. For example, SX Dra. It has a good range and it's easy to find if you star hop, but it hasn't had an estimate, visual or otherwise, for over a decade. I've been thinking of asking the charts team if they can generate a sequence for it and others. These look like worthwhile targets. 

SX Dra

While observing eclipsing binaries can be a lot of fun visually (and are excellent candidates to bring new people into variable-star observing), especially the ones with big, fast eclipses, be a little careful about assuming that (a) such visual estimates have good scientific value, and (b) the lack of observations in the AAVSO International Database means they are underobserved.

In general, a CCD time-of-minimum is a hundred times more accurate than a visual estimate, and it is unbiased (there is no hint of eclipse expectation).  So if you see several recent CCD ToM for a particular star, then expect a simultaneous visual ToM to be ignored by the researcher.  For visual work, to increase the value of your observing, check to be sure the star is not already covered by the CCD observers.

The AAVSO articles by Gerry Samolyk giving times of minima are important records of AAVSO activity, but the German Lichtenknecker database is far more extensive, and should be your first choice when setting up an eclipsing binary program:

If you search that database, you will see that SX Dra has lots of (mostly visual) timings and a very nice (O-C) diagram, including 4 recent CCD timings, even though there are no reported AID observations. SX Dra is an interesting system as the primary star is a delta Scuti variable with 0.04V amplitude and 63min period.