A miscalculation of reciprocity failure meant that the neg was quite underexposed and with a straight print the sky was just base white and only the main trunks of the trees showed. Burning in the sky/trees using a carefuly cut mask didn't improve things much. I then had a rare moment of inspiration and tried a Sabatier solarisation which I think gives it the required spookiness. I need to find some paper that will give more contrast in the stones.