SIGHTING REPORT UFO sighting at spital,wirral

I saw a dark disk moving across the face of the half moon in my 12" telescope.It's diameter was ~ 25 arc seconds.It crossed the illuminated moon in ~15 seconds ,direction roughly from west to east.It's speed was ~1.6 arc mins / second.

the object moved at constant velocity and the shape did not change
(as might be expected of a partly deflated weather balloon).

In 50 years of looking through many telescopes I have never seen anything like this object.At first I thought it was a weather balloon but noticed that the leading edge, in the direction of travel, was flattened ...it was not a full circle. Then I thought it was a small asteroid but it was far too regular in shape.I have never seen a satellite this shape.If it was a satellite, given it's tangential speed the orbital period would be ~3.7 hours...unusual.This would put it 7,000 miles distant and give a diameter of 0.84 miles.I conclude that it was not a 'satellite' in Earth orbit... it would have been spotted.
So what was it? It was an artificial object somewhere in the atmosphere.There was no jet exhaust.These show up clearly as heat ripples when a jet plane crosses the moon. Any suggestions ?
Any similar sghtings ?

Professor D P Gregg (retired)