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Actually the old celeston manuals state exactly what you are seeing, that if you shine a torch down a SCT you will always see marks, regardless of how well its been cleaned. It doesnt affect performance, and in truth you will try endlessly to get rid of it. I am speaking from experience here, my old scope didnt have coatings on the corrector so cleaning it wasnt such an issue, but still could never get rid of all the marks when shining a torch down it. In the end I decided to finally read the manuals, and promptly gave up. And it never affected performance.
But it does look like someone has cleaned your scope in the past, the marks look circular, as if someone has whiped a cloth (say clockwise) around the plate. This is a mistake in that if the cloth was dirty (heaven forbid) you leave a nice circular scratch right around it. A profesional always whipes it out in a straight line from centre to edge.
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