OneLens- took my 500mm Nikkor f8 mirror lens out this afternoon to our local pond and found Henry the Heron washing his feet. I have owned this lens for a number of years, but have hardly ever used it. Although this shot was handheld, a lens of this length does need to be supported with either a tripod or monopod. The way to ensure a sharp shot is to put your camera into High Speed burst mode and take several bursts. Generally if you rely on a single shot then more often you will get some degree of camera shake due to pressing the shutter release. With a burst mode you will get a few frames sharp once the firing has started.
That's a great tip, Vincent! Looking forward to trying out the burst mode the next time I go out without a tripod.