High-resolution imaging requires your telescope to be properly cooled and its optics to be accurately collimated. In addition, sharp focus is essential too. However, even if you get all of these factors correct, your results can still be thwarted by atmospheric seeing. Assessing the nature of the prevailing seeing and understanding factors that affect it is as much a part of high-resolution imaging as any of the physical instrument settings. The subjective assessment that comes with practice is important too, as conditions can change quickly.