Measured dipole direction in Galactic coordinates as a function of the maximum temperature multipole used in the analysis, ℓ_max. We plot the results for the four data combinations discussed in Sect. 4: 143 × 143 (▾ symbol); 217 × 217 (▴ symbol); 143 × 217 (× symbol); and 143 + 217 (+ symbol). The CMB dipole direction β_∥ has been highlighted with 14° and 26° radius circles, which correspond roughly to our expected uncertainty on the dipole direction. The black cross in the lower hemisphere is the modulation dipole anomaly direction found for WMAP at ℓ_max = 64 in Hoftuft et al. (2009), and which is discussed further in Planck Collaboration XXIII (2014). Note that all four estimators are significantly correlated with one another, even the 143 × 143 and 217 × 217 results, which are based on maps with independent noise realizations. This is because a significant portion of the dipole measurement uncertainty is from sample variance of the CMB fluctuations, which is common between channels.