Astronomical Society of South Australia (ASSAU)
Fri, 02/17/2023 - 07:28

Bob Nelson’s O-C data base is a unique resource to all eclipsing star observers.  For many years, Bob collected the observations and updated the workbooks on his own.  In the last several years I joined him in this work.  I have just completed the 2023 workbook updates and they are now available on the South West Research Institute website (, and soon will be on the AAVSO site too. 

I have no idea how Bob managed to do the workload on his own for so many years.  It took me most of January to complete the workbooks updates.  I am looking for some people to assist in keeping this database alive.  It is important that more than one person is working on the project not only to spread the load but to ensure more than one person knows what needs to be done – succession planning (I am 72 yo). 

The tasks include:

  • Trawling through Journals to collect new O-C observations;
  • Collating the observations;
  • Annually (at this stage) adding the new data to each workbook in the database;
  • Undertaking analysis of the data as required.

If you are interested in assisting with this work, please contact me at  Note I live in South Australia so allow for the time zone difference when waiting for a reply.

Robert Jenkins

Bob Nelson’s legacy

Hi Robert,

 I will put my hand up to help update Bob’s spreadsheets. I’ll email you directly when I get home. Currently my wife and I are in Ushuaia, Argentina about to start a cruise to Antarctica. Home in mid-March. Cheers,


American Association of Variable Star Observers (AAVSO)
Bob Nelson's O-C Database


Your effort to maintain Bob Nelson's O-C database is greatly appreciated by those of us who regularly investigate the secular behavior of eclipsing binary systems. 



British Astronomical Association, Variable Star Section (BAA-VSS)
Bob Nelson's O-C Database

Hi Robert,

Since December 2020 I have been publishing my O-C observations in the British Astronomical Association Variable Star Section Circular (BAAVSSC). So far I have published 72 observations which can be found in the following editions: VSSC187, VSSC188, VSSC191, VSSC193, & VSSC195. As I am the only observer currently publishing there, its possible these observations are getting overlooked.

Tony Vale


Astronomical Society of South Australia (ASSAU)

Hi again Tony


I have added all of your observations to the master files I have.  This data will show on the next update of the workbooks into SWRI and AAVSO.

I will make sure BAAVSS p[ublications are now searched during the updates to the workbooks.  

Note if you need to contact me directly, use