I was fiddling around last night, trying (not very effectively) to take portraits with flash lighting on Ham Hill, when I had a few seconds notice of this photo as I heard the helicopter. I knew that I had to try to grab a shot as it crossed the sunset. Sadly though, I had no time, or my brain didn’t work fast enough, to think about shutter speed for the shot, and being in portrait mode at the time, I had the aperture wide open. All I managed was to expose for the sky to get the silhouette that I wanted. The result is that the shutter speed was much too high, so there is no blurring of the rotors. normally essential for helicopter shots. The shutter speed should have been 1/125 sec or less for a Sea King and in fact it was 1/4000 sec.
Because the Sea King is in the distance, I might just have got away with it.