This was a question I had when I first started doing time series of CV’s. I had previously done lots of asteroid photometry for determination of light curves and spin periods. Several people working the same asteroid at the same exact time was not very valuable. A lot of communication was necessary among asteroid photometry folks to spread out the targets for the most value.
For time series of cataclysmic variables, the answer to the question is different. Several people working the same CV at the same time is still valuable. The periodic signals that are gleaned from CV light curves are buried in lots of other signals and the “noise” of CV flickering too. If several folks are working the same CV at the same time the strength of the periodic signals we are trying to find are amplified and are measured with greater accuracy. Simultaneous observations also show us the small magnitude offsets between different observers’ systems so all nights of those observers can then be shifted to be on the same scale. That helps to pick out the longer term periodic signals that need long time series to see.
No need to worry that your data is redundant if others are working that star too. For CV’s, it all helps. Thank you for your contributions! There have been a lot of recent papers that have relied on CV photometry submitted to the AAVSO. Many more to follow.
Clearest skies,
Walt