IMPORTANT NOTICE:

From July 1998 on we present the tipper tau data statistics with a time normalization. Before, just the observed data had been used and gaps had been ignored. There are gaps when the tipper is not in operation (e.g. during a snow storm) but there are also gaps due to bad fits even when the weather is excellent. The new scheme takes both cases into account. The gaps without data are counted as bad weather or high tau. In case of bad fits, a searching algorithm looks for good fits within +/-3 hours from the current slot and uses the corresponding tau value if it finds one. Therefore up- and downscaling is possible.

There are a few months which suffer from extreme downscaling due to extended periods of the tipper being shut down. This usually happens only during the summer months because of maintenance at the telescope site.

All previous data (March 1995 to June 1998) have been rescaled accordingly so that a direct comparison of all plots is possible. In addition to the changes in scaling, we have also improved the graphs by adding more precise date information and percentages for selected tau's. In two cases, (March 7-13 1999 and March 18-19 2000), we included taus that we scaled. They were obtained from spectral line observations during brief periods when our taumeter was offline and we were observing.