The problem of night-photos is, that the cargo area is grown very much in the last five years and the the UPS-aria is far in the back. Seen from the Terminal you first see DHL, then LH-Cargo and others and at last UPS with Channel Express. Most of the UPS-aircraft you cannot recognize. At night you only can make photos when the planes are taxiing to RWY14L - this begins at about 3.30 AM in the morning, the 747 takes off at 6.00 AM.
Here are some Infos on UPS at cologne (for photographers):
on sunday the 747-100/200 is landing at about 12:30 PM and in the afternoon 2 B767 are landing. Then photos can be made without the problem of darkness.
Further on sunday the whole european 727-Fleet of UPS is parked at cargo area 2. They can be watched from a forest near RW25 (near Cargo Area 2 / from the Terminal you can´t see them because to far away and buildings in front of).
CGN is not served by 757 - UPS uses only 747/767/727.
Hope these infos will help someone.
I usually don´t make photos, but perhaps I will try it next time.