Galaxy crescent moon on a forearm

The moon has been wrong all week, too thin on the Tuesday and fat as a cheese by the Thursday, and Dad says it is only the haar playing tricks. I have been up at the north light doing your watch because Hamish's knee is still bad and nobody else will climb the stair without complaining.

Up there the sky goes properly dark, the kind you never get in Leith. I took the old star chart from the drawer in the signal room and tried to match what I could see. Last night, with the cloud off, the crescent hung low over the Skerry and I swear the inside of it was not black at all. It was full of colour, blue like the bottle glass on the windowsill, and a pink smudge where the dust would be, with small white specks like someone had flicked a brush. I counted eleven before the fog came back.

I wrote it in the log, which Mr Anderson will not like, because the log is for weather and tides and nothing else. Then I thought of you out past the shelf, where the sky is nothing but stars for a hundred miles. You told me once the moon only borrows its light from the sun. I sat on the cold step for a long time after that, with the lamp turning over my head.

So I am sending this with the chart folded inside, and a page torn from the signal book. Keep it somewhere dry. When the cloud lifts, look for the part of the moon that has no sun on it. I think that is the best part. Love, Morag.