 Tizard was aware that tests showed an observer would only be able to see an aircraft at a range of about 1 @,@ 000 feet ( 300 m ) , perhaps 2 @,@ 000 feet ( 610 m ) under the very best moonlit conditions , an accuracy that the Dowding system could not provide . Adding to the problem would be the loss of information from the ROC , who would not be able to spot the aircraft except under the very best conditions . If the interception was to be handled by radar , it would have to be arranged in the short time between initial detection and the aircraft passing beyond the CH sites on the shoreline . 
