We report new observations of the intermediate-frequency peaked BL Lacertae object 3C 66A with the MAGIC telescopes .
The data sample we use were taken in 2009 December and 2010 January , and comprises 2.3 hr of good quality data in stereoscopic mode .
In this period , we find a significant signal from the direction of the blazar 3C 66A .
The new MAGIC stereoscopic system is shown to play an essential role for the separation between 3C 66A and the nearby radio galaxy 3C 66B , which is at a distance of only 6 ^ { \prime } .
The derived integral flux above 100 \mathrm { GeV } is 8.3 \mathrm { \% } of Crab Nebula flux and the energy spectrum is reproduced by a power law of photon index 3.64 \pm 0.39 _ { stat } \pm 0.25 _ { sys } .
Within errors , this is compatible with the one derived by VERITAS in 2009 .
From the spectra corrected for absorption by the extragalactic background light , we only find small differences between the four models that we applied , and constrain the redshift of the blazar to z < 0.68 .