I've been doing some research to try to find eclipsing binary stars that don't have many estimates in the AAVSO database and something has been confusing me for a while. Many stars have up to hundreds of estimates listed, often from decades ago, but all of the estimates are "0.0" magnitude, and all are by "BM." I was wondering if anyone could tell me why? Just curious, and thanks in advance.
Years ago, there were no comparison stars available for EB stars that were observed. An arbitrary scale of "steps" was used instead. For these type of observations, 0.0 was entered into the magnitude field. The step value for the estimate can be found on the comments field. These observations were used to determine times of minima.