Continuous readings, by means of automatic indicators, of either the actual or the predicted ranges and azimuths of moving target at every instant and for any distance from 1,000 to 15,000 yards and through an azimuth of 160 degrees, are clearly presented at all times. The ranges are read in scales of 10-yard steps, and the azimuths for each .01 degree are traversed. The corrected ranges for the various guns served by the instruments, either actual or automatically predicted for any interval of time, are constantly communicated to the various guns whose fire is being directed by the observation instrument.