I agree with Ben that using filters at night is a recipe for introducing flare.
Although it very much depends on the filter used.
Have a look at:
UV filters test - Introduction - Lenstip.com to see the differences.
It is a good guide for selecting protective filters. Good filters are not cheap and expensive filters are not always good.
You will see in the individual tests the flare results of the filters.
Unfortunatly , filters are not "just another piece of glass" that you can screw on your lens without any negative influence on IQ!
- Bert