The image frequency setting did not work prior to the latest firmware, v1.09
Set the seconds per frame to 1800 (=30 seconds x 60 seconds/minute)
And you would set start and stop to 05:30 to 20:30
I think I did this with 5 minute intervals (300 seconds/frame) a while back - didn't keep the results, because camera was getting hit by sun and washing out the pics, but it did work at 5 minutes