Strip setup on the HBA map of NGC 891. The map has been point-source-subtracted and masked. The six strips (UL, UM, UR, LL, LM, and LR) are indicated with thick black lines. A similar setup is used on all galaxies during box integration with NOD3. Central boxes are part of the lower as well as the upper strips. Left strips have a positive offset, and right strips have a negative one. Individual boxes (thin white lines) have a height of 10″ and a width of 177″ (as listed in Table 5).