I agree, it looks a lot like camera shake. I often shoot with my D-FA150-450 handheld, usually for birds in flight. I put the camera in TaV mode, and rarely shoot at a speed lower that 1/1000 and almost always a f8, where I've determined my lens resolves the sharpest image (note, there is not a lot of IQ difference between 5.6 and 8, so if it's a cloudy day, I'll open up my f-stop for more light). I set the Auto ISO cap at 12800. Personally, I found that camera shake with the D-FA150-450 is the number one reason I don't get a sharp image.
If you want figure out which combination of shutter speed, aperture and ISO work best for you, you can try this test. Mount the camera on a tripod, put the camera in AV mode, set the aperture to what is sharpest on your lens (usually f8 or f11), set the ISO at 100. Find a static object about 100 to 200 feet away from you, use Live View to focus on the subject, and take the shot (I like to test my camera lens by shooting the tops of power poles. There's always text and phone numbers on the equipment, so I know right away if my image is sharp or not. And it's not something I can see with the naked eye from a hundred or two hundred feet away). The resulting image is now your baseline image, and should be in the "tack" sharp category. (This is the key, you have to establish a baseline tack sharp image, whether you use Live View or Single Spot AF is up to you, I like to use Live View personally). Once you've established the baseline image, take the camera off the tripod, put it in TaV mode, keep your same aperture setting, start with a shutter speed of 1/500 and start taking handheld images of the same subject, increasing the shutter speed with each image, until you get an image that is equal to your baseline image. Once you have that, you know the neighborhood of settings you'll want to start with (there will always be variations based on a million outside factors). I recommend saving those settings in one of the USER modes, so you can just jump to them without have to remember them (then you can make minor adjustments as needed based on "environmental" conditions - i.e. shade vs. sun). You can do the same thing, using the monopod. Presumably the monopod will add another level of stability between the tripod technique and the handheld technique.
I find that the problem most people have using a long lens at the long end, is they haven't practiced enough with it to understand it's limits and it's strengths. A Super telephoto zoom is a lot less forgiving than a stand telephoto zoom and even more so than standard zooms.
When I first got my D-FA 150-450 lens, I found this particular PF article to be incredibly useful in learning how to really use this lens. I started with this and then made changes to the settings based on my shooting workflow style.
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