The design of the DDRAGO wide-field imager for the COLIBRÍ telescope

We present the design of the DDRAGO wide-field multi-channel imager for the 1.3-meter COLIBRI telescope for the Observatorio Astronomico Nacional in Mexico. The instrument is designed to provide initial follow-up of GRBs detected by the ECLAIRs instrument on the SVOM satellite. DDRAGO has blue (gri) and red (zy) channels which use 4k by 4k CCDs and give fields of 26 arcmin. It also delivers a faster infrared (JH) beam to the CAGIRE imager which uses a 2k by 2k detector and gives a field of 22 arcmin. DDRAGO is a descendent of the successful RATIR imager, but the optical design is significantly more complex to allow much wider fields. We summarize the optical, optomechanical, structural, and control design.