PZeller66 wrote:

Thanks for the confirmation! I was starting to think that my eyes were
playing tricks on me early that morning.

I had the same impression when I saw it, too.

I'm assuming that the constant look to its brightness was because of it's
orientation. Maybe I was first seeing it at a nearly right angle to its axis of
rotation, and then when it was closer to the horizon I was seeing it more from
the side, tumbling end over end.

That's my guess, too. It's the upper stage of a Russian Zenit-2
booster; astronautix.com describes that stage as being 3.9 meters
in diameter and 11.5 meters long, which allows a lot of change
in its observed area as it tumbles. My guess is that it did
something odd when it vented excess propellant after reaching
orbit.

I spotted it again less than an hour ago, in clear skies. The
flashing is still impressive.

--Bill Thompson