The use of deep blank fields is crucial for the correct operation of the GTC. Hitherto, the list of deepest blank fields was the compilation by M. Azzaro for the ING telescope. However, they demonstrated to be shallow for large class telescopes. We used TESELA, a new VO tool, to determine blank fields for their use with OSIRIS at the GTC. The result is a catalogue with the deepest blank fields known so far, which have demonstrated to be extremely useful for medium and large size telescopes at the northern hemisphere.