  EFOSC2 (the European Southern Observatory Faint Object Spectrograph and
Camera v2) is one of the workhorse instruments on ESO's New Technology
Telescope (NTT), and is one of the most popular instruments at La Silla
observatory. It is mounted at a Nasmyth focus, and therefore exhibits strong,
wavelength and pointing-direction dependent instrumental polarisation. In this
document we describe our efforts to calibrate the broadband imaging polarimetry
mode, and provide a calibration for broadband B, V, R filters to a level that
satisfies most use cases (i.e. polarimetric calibration uncertainty ~0.1%). We
make our calibration codes public. This calibration effort can be used to
enhance the yield of future polarimetric programmes with EFOSC2, by allowing
good calibration with a greatly reduced number of standard star observations.
Similarly, our calibration model can be combined with archival calibration
observations to post-process data taken in past years, to form a EFOSC2 legacy
archive with substantial scientific potential.
