A noiseless and oscillating bright light in the eastern sky was moving from the south to the north.

A hour or so prior we saw the ISS crossing the sky to the south, that was very distinguishable. I was trying to photograph an iridium flare to the east when later my wife noticed a bright enough light (-2M) approaching from the south.  We though this could be the ISS again, but it was too soon.
We noticed it in the southeast and it was moving north at the pace that the ISS would.  The only difference is that this light was oscillating in brightness as it was moving and it would fade to about half the brightness before becoming bright again.  I thought this would be tumbling iridium, but from what I understand tumbling iridium is not that visible to the naked eye.  The object made no sound and had no flashing lights the way a commercial plane/jet would have.  As soon as it got almost 90 degrees east it slowly disappeared.
I had my camera ready and captured 30 seconds of the final moments before it disappeared.  The original photo will be e-mailed for further investigation.