Trying to be positive when there have only been a brace of sunbeams all August so far, I have been tinkering with the overcast shadow method. The theory being that plenty of light filters through the overcast clouds and that a thin blade can be used to average the source of this light, ie. the sun. It is better than nothing, sometimes, but it is important to be aware that the shadow will be thrown opposite the brightest light and there are no guarantees that this is where the sun is. Uneven cloud or tree cover are just two of the things that can throw it completely.