ok after talking to a rep that sells the off delay timer I am confused. Ha. He thinks I need an ON delay timer as this would delay the lights from energizing for a time interval of my choosing then keeping the lights ON. Is this your understanding of the OFF/ON delay timer?
An On-Delay would close only after a set amount of time. If the command signal is chattering, it basically will fail to close until the chattering stops because the chatter is constantly resetting your timer. I suppose that might work eventually though, but your delay time would have to be set for longer than the time it chatters, and you don't know what that is (yet). So let's say it is chattering for 15 minutes, your contactor would not energize then for 15 minutes as the photo eye voltage chatters.
An Off-Delay time would close immediately, then if the command signal chatters, it remains closed for a set time, let's say a second. As long as the chatter cycle is less than a second, the output never changes. But you don't have to worry about how long it is chattering, it doesn't matter.
By the way, I should have also mentioned that sometimes this can happen if the lighting you are controlling is bright enough to be detected by the photocell controlling it. In other words it gets dark, the cell turns on the contactor, the light hits the cell, it turns off. Repeat to destruction. it might be a simple as moving the photocell.