Hi TS
When shooting at night, depending on your UV filter, u may get flare or ghosting light in your image. cheap UV filter tend to be prone to reflect light inbetween the lens and the filter causing a ghost flare in the picture.
advise is to remove filter during night shot where there are alot of strong light source (ie spot/flood light) else pay more for better filter. personal experiance is that, I gotten a cheap $20 emoulux uv filter, gave alot of flare and ghosting light spot in my picture. after stepping up to better filter like B+W, the encounter with flare and ghosting at night reduce drastically, flare sometimes still happen when my lens angle wrong and staring quite directly at a strong light source, easily overcome by reposition.