Sometimes this is due to having the magnification of the scope too high! There’s a tendency in thinking that the higher the magnification, the better the resolution! Not so in most cases! Be patient in your adjustments as sometimes it needs to be just ever so slightly on the object to eventually get a clearer view. Other times, it could just be the angle at which you are approaching the object. Once at least two of those factors are ruled out, then you should look at the quality of the aperture itself.