The DSLR And The UFO
I can only surmise that the aliens were employing some form of force field to shield them from observation. Perhaps it was not working very well, hence the blur. One of the salespeople here suggested that this was just dust on the sensor but the photographer assured us this was not the case. I rang up the Air Force to confirm the sightings but they are a rude lot and rang off. And the language...
Just on the off chance that you are also seeing alien craft when you take pictures of a clear blue sky, make the experiment of also photographing a clean light grey piece of paper. If the spots are still there they are likely on your sensor. If the spots move it can be a sign that they are small movable particles that are shifting around on the sensor surface - perhaps moved by the sensor cleaning mechanism in your camera - or they are small bugs moving on the grey cardboard. Persist.
Just this week I sold a kit to a person for sensor cleaning that is made by Promaster. it consists of two wands with clear plastic gel pads on the ends - one is a large stamping block and one is a small pointy poking one. The soft plastic is meant to pick up particles from the surface of the sensor - you then transfer this to an even softer plastic pad to remove it from the wand. When the sensor is all clean, you wash the pads and wands in distilled water to get rid of the dust, put it away, and are good to go again.
I hope it works - we'll get a report from the customer in due time. I am not sure if the pads will remove real UFOs but at least they will go back to Betelgeuse looking a lot fresher and cleaner.