Scilly, the nearest part, is 28 miles off Land's End. From above Sennen it's 30 miles to the main Islands. Today they were exceptionally clear, the visibility must have been around 50 miles (assuming you were a fair height above sea level!)

Anyway, the bottom pic on http://www.turnstone-cottage.co.uk/BH.html shows Scilly from near the Sennen Lookout. Yes it's fuzzy, but we are looking at something that is very small to the naked eye taken by a compact camera with the maximum 40X zoom (only 8X optical).

Lovely wave now with a little shelter.

Graham
Penzance