Comparison between the integrated EWHα (top panel) and Hα flux (bottom panel) repeatedly measured in different observing runs. Red symbol refers to measurements taken in April and May 2010 at the 1.5 m. Blue symbols are 1.5 m vs. 2.1 m measurements. Green symbols are 2.1 m vs. 2.1 m repeated measurements. The dashed lines give the 1:1 relation. The object with deviating EWHα was checked on SDSS nuclear spectroscopy and found to be consistent with the 2.1 m measurement.