Half of moon fluctuates in luminosity and hue randomly, why?

[sonoffeanor]

I looked up at the moon with several friends and family members and the moon would gradually get brighter for 30 seconds. It would stay bright for a couple minutes and then dim down also large dark spots randomly appeared on the visible part of the moon. I did some research and read that this might be a Transient Lunar Phenomena event but most of the descriptions were just small spots of the moon lighting up. The one I witnessed, the whole visible part of the moon got brighter. I confirmed it with other witness, so I know I'm not crazy. Could it be a Transient Lunar Phenomena and if so what were those black dots? The other witnesses keep annoying me and tell me it was a UFO, so any explanation would be nice to get them of my back.

 

[Drakkith]

Honestly it sounds like it's just clouds. Not the normal puffy ones maybe, but maybe the large hazy ones that gradually build up as they move in.
At what point in the sky was it? High overhead, near the horizon, etc.

 

[Barakn]

Sounds more like biological optics to me. The brightening and dimming could be explained by some sort of combination of dark adaptation, the moon moving onto and off of the blind spot due to eye movements (saccades), and saturation ("bleaching") of over-exposed retinal pigment. The dark spots are probably floaters in the vitreous humour of the eye.

 

[sonoffeanor]

The moon was near horizon. It sounds close to what Drakkith said. Thanks a lot. It may also close to Barakn or even a combination of both. Thanks guys any type of answer is great as long it isn't a UFO :P