Long-term multi-wavelength light curve of 1ES 1215+303 from 2009 December to 2011 May. The vertical line shows the beginning of the MAGIC 2011 observation campaign. a) In the MAGIC light curve 2011 data are binned in 5-day intervals. 2010 data are divided in January − February and May − June bins. b) The Fermi-LAT light curve (1 − 100 GeV) has bins of 14 days and the points with arrows are upper limits. c) The Swift/XRT light curve is derived from the target of opportunity observations performed during the MAGIC observations and archival data. d) The R-band light curve shows hourly average flux of the source, the error bars are smaller than the symbols in most cases. e) The optical polarization (filled circles, left axis) and polarization position angle (triangles, right axis) are hourly averages. f) 37 GHz radio light curve from the Metsähovi radio observatory.