A sensitive image orthicon slit spectrograph has been developed for the investigation of aurora and night air glow, particularly with respect to their time changing characteristics. The equipment design meets the following specifications: sensitivity, 20 photoelectrons produce a detectable signal; dynamic range, 200:1; resolution, 5–30 Å; spectrum coverage, 3800 to 8200 Å; and typical exposure required on a just visible aurora, 1 sec, on night air glow, 10 sec.