First of all, lets explain this on a smaller scale.
This is a street lamp outside my window. I know it's a street lamp, I checked, you can even see the pole. Anyway, zoomed all the way in, this is what my camera can focus on. It being dark and the light being bright, the bulb creates spikes, it's already bright enough to cause problems for our lenses.
If we introduce a window however, the camera has to decide to focus on the bright light, the grimy window, the reflection in the glass… it tries its best but it creates two images, the image in the window being more detailed that the image beyond it. You can see the shape of the lamp and even the bulb itself on the ghostly image.
In my experience, the ghostly second image has more detail than the actual light source. In the video I took of the moon (it's in one of the NN videos, number 7 I think), the moon itself was just a bright white disc to the camera, but the image on the window revealed the large features, the contrast on the surface etc.
However, we've got another element to add here - clouds.
Count the number of challenges the camera has now: Sun/Moon, reflection in window, dirty window, and now a whole bunch of clouds. We can't expect it to be crystal clear in focus for all of those things at the same time, it just does its best.
But not all of those elements are equal. The reflection in the window may be detailed, but it is nowhere near as bright, and when placed against clouds of a similar colour, you'll have a hard time to pick anything out. The sun itself of course is really rather bright, cuts through much of the thicker clouds to a certain extent, but whenever there is a chance to see the 'second sun', it follows the same pace and distance from the sun, due to angles of the camera or more likely the window itself (windows don't wobble like cameras after all)
Once you've worked out that this is a video filmed through a window (we not only see the window frame at 45 seconds or so, but we also see dirty windows in places. It's a little hard to pick out, but watch the bottom right corner of the video from 1:15ish, you can see the dark clouds in the background, and some out of focus dirty windows appearing to float on a layer in front of the clouds), and have tried it out a few times yourself (always worth it), you'll get the hang of spotting each thing going on, you can track the image over the course of a video, and so on…
Essentially, when you know a bit about it, there's not much of a mystery left to talk about.
And here, for the heck of it, is an out of focus lens flare that I will now attempt to pass off as a planet, despite it being an out of focus street lamp.
Also, unless there's a sandbox kicking around, just go for the edit. Works the same way as these comment boxes, there's a preview button, you don't have to save anything, if you do we can revert your edits. Or post it here I guess.
That's enough typing from me for now.
