[popo]

That sample looks to me like you could improve your technique before we even start to look at the lens itself. I can only guess at the settings used, but presumably high ISO and/or significant underexposure will give you that noise pattern. The image doesn't look clear, could it be motion blur? From the degree of diffraction spikes a smaller aperture was used?

For that type of shot, ideally you would manually force a lower ISO setting which can result in longer shutter speeds. A tripod may be required. Especially if you reduced the aperture that can contribute to needing even longer exposures.