El texto de Ronald Hill:

Whilst not attempting to contradict any of the suggestions of the disc bring
a UFO it is interesting to apply a histogram enhancement to the pictures on the site.
The object then shows a very close resemblance to the moon, The area of
illumination is comparable to that of the moon on the 21st of November (2 days
before full moon) and the dark markings closely resemble the lunar 'seas'.
try it and see what you think.
Ronald Hill