A photograph of an object does not necessarily look the same as the real object. There are various optical imperfections, which are impossible to avoid by both the designer of the optical system and the photographer taking the picture. One of those imperfections causes lens flare.
Some flat-Earthers noticed the existence of a ‘mysterious celestial body’ next to a photograph of the Sun or the Moon. They would use such sightings to ‘explain’ various celestial phenomena which cannot be readily explained in the flat Earth model, like eclipses. They are wrong. The ‘mysterious celestial body’ was merely a lens flare.
Lens flares happen because each of the lenses in a camera system cannot perfectly transmit light, but reflects some light away. Some lenses also refract bright light at an unintended angle. If the object is very bright, and especially with a dark background, the unwanted reflection and refraction would happen with multiple lens elements, and the light hits the camera sensor in the wrong location, registering the object at a false position, with lower intensity.
Phone cameras notoriously have very low flare resistance. It is easy to replicate lens flare using any phone cameras, especially with a bright object on a dark background, like any street light at night. In most cases, lens flare will appear at the opposite position from the object, relative to the center of the frame.
- Lens flare – Wikipedia