Many of the complexities and problems with the present SKE could be avoided by replacing it with a fixed KE. The orientation problem is solved by making the KE in the form of a plate with a sharp-edged hole in – behind some part of the edge of that hole the Moon could always be parked so that just the DS peeked out.

The present size of the Moon on the CCD is a bit too big for this to work. We need to understand which part of the system to rebuild in order to get the Moon to be smaller (perhaps 50% smaller) on the same CCD – or perhaps to get a bigger CCD. The present system is ‘short’ which means that the edges of the field and the centre have problems being in focus at the same time, so a larger CCD would have worse problems (but the worst affected areas would be behind the mask!)