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tokens: atmospheric dispersion corrector in the fall of 2009, reducing the crosstalk below 1 per cent. Periodic monitoring of the crosstalk confirms that it has remained stable since 2009. However, higher crosstalk levels were likely present (with levels as high as 5 per cent) during the first three semesters of MiMeS LP observations. The absence of any significant impact of crosstalk on most MiMeS observations is confirmed through long-term monitoring of TC targets as standards, and is addressed in Section 4.2 . 5 The crosstalk evolution and mitigation is described in more detail by Barrick, Benedict Sabin ( 2010 ) and Silvester et al. ( 2012 ). Change of the ESPaDOnS CCD: until semester 2011A, ESPaDOnS employed a grade 1 EEV CCD42-90-1-941 detector with 2k × 4.5k 0.0135 mm square pixels (known as EEV1 at CFHT). This was replaced in 2011A with a new deep-depletion E2V CCD42-90-1-B32 detector (named Olapa). Olapa has exquisite cosmetics and much less red fringing than EEV1. Another major difference is that Olapa's quantum efficiency in the red is about twice as high as with EEV1. Commissioning experiments by CFHT staff, as well as within the MiMeS project, were used to confirm that observations acquired before and after the CCD replacement are in excellent agreement. This is discussed further in Section 4.2 . 2.4 Narval 2.4.1 Instrument Narval 6 is a near-twin of ESPaDOnS installed at the 2 m TBL in the French Pyrénées. It is composed of a Cassegrain polarimeter unit similar to that of ESPaDOnS, and a similar spectrograph located in the TBL coudé room. Compared to ESPaDOnS, the instrument was only adapted to the smaller telescope size. Small differences include the diameter of the entrance pinhole of the Cassegrain unit (2.8 arcsec for Narval, versus 1.6 arcsec for ESPaDOnS) and the lack of a fibre agitator. However, the sampling of the (sliced) pinhole image is identical to that of ESPaDOnS. The CCD used at TBL (a back illuminated e2v CCD42-90 with 13.5 μm pixels) differs from that used at CFHT. However, each Narval spectrum also captures 40 spectral orders covering a similar spectral range (370–1050 nm) with the same resolving power of about 65 000. All other technical characteristics of Narval are effectively identical to those of ESPaDOnS described in Section 2.3.1 . 2.4.2 Observations Observations of MiMeS targets with Narval were initiated in 2009 March, and continued until 2013 January. A total of 1213 h were allocated to the MiMeS programme, first in the framework of three single-semester programmes and then as an LP for five additional semesters (all of these observations are hereinafter considered to be ‘LP’ observations). TBL programme identifications associated with MiMeS were prefixed by the letter ‘L’, followed by the year (e.g. ‘12’ for 2012) and the semester (1 or 2 for semesters A and B, respectively), then ‘N’ for Narval, and the ID of the programme itself (e.g. ‘02’ in the case of the LP). The MiMeS Narval runs are thus L091N02,