Redtail home - Temp problem

[maccaw1]

Ok, I'm getting ready for my new Redtail and am getting her home ready.
I put an under tank heater on the bottom of a 55 gal aquarium at one end along with a 55watt bulb for basking. My problem is that the temp on the basking side is only 83.5 degrees and on the other side it's 78.5 however under her hiding place on the backing side it's already 94.2 deg propably because of the under tank heater. What should I do?