I need help identifying a blob.
Last night I took a picture of Polaris, and there is a weird blob in it that I can't identify. Star charts and other pictures on the 'net do not show this blob. I took three pictures (with slightly different positions) and the blob has the same shape and position (relative to Polaris) in each. The blob does not exist in other pictures that I took (pointing in completely different directions).
Taken with a Canon t5i, 300mm lens, 3 minute exposure on a motorized equatorial mount. Viewing conditions were terrible, with lots-o-moon and smoke from forest fires. From Colorado.
Polaris is the brightest star, slightly left and down from center. Yildun, the next star in the handle of the little dipper, is near the upper left corner. The blob in question is very near, and slightly up and to the left of Polaris.
Simple Lens Flare: I don't think it's lens flare (LF). With LF, you can draw a straight line through the photo where the flare, the bright object, and the center of the photo all line up. Also, the LF tends to match the shape of the bright object. I don't think it's LF because the blob doesn't line up with the center of the photo and a bright object, and there are no bright objects that have the same shape as the blob (with that weird tail to it). Also, I have three photos with the same blob. In each case, Polaris (the brightest point in the photo) moves slightly because the camera moved slightly but the blob moves exactly with Polaris and not somehow relative with the center of the frame.
Under careful analysis, there IS lens flare, but it is where you'd expect it and not where the blob is. If you draw a line though Polaris and the center of the frame, there is a flare on the opposite side of the center and the same distance away from the center as Polaris is.
Schmutz in the camera: I don't think it's dust/dirt in the camera/sensor. If that were the case then I would have seen it in other photos from the night, and I didn't. Also, the blob would have stayed in the same position in the frame and not moved with Polaris as it did in the 3 different photos that I have of it.
Not-So-Simple Lens Flare: Maybe. Although I cant imagine how this would happen unless some lens elements were not radially-symmetric and/or elements were not lined up on a common axis. But I don't know everything about camera design so maybe this is possible?
There's a new blob in the sky: Possible. Although I think the odds of "user error" are much higher. Maybe someone else wants to take a new photo of Polaris? (wishful thinking)