the effects of atmospheric seeing were indirectly responsible for the belief that there were canals on mars. in viewing a bright object such as mars, occasionally a still patch of air will come in front of the planet, resulting in a brief moment of clarity. before the use of charge-coupled devices, there was no way of recording the image of the planet in the brief moment other than having the observer remember the image and draw it later. this had the effect of having the image of the planet be dependent on the observer's memory and preconceptions which led the belief that mars had linear features.