oval object with no sound or lights that blocked out stars as it moved from horizon to horizon

Even though it has been many years since my friend and I saw the object, I thought it would still be a good idea to record the information here.
 It was on a late night drive home from a job our band had played in Vermont during the summer of 1985, and as we were driving on dark road just back into NY, we both caught a glimpse of the stars beginning to disappear in the totally clear sky. We pulled to an overlook parking lot and got out of our truck and watched it.
There were no lights, no sounds other then crickets chirping, as we watched, the stars disappeared slowly behind a solid black shadow. We estimated that the object had to be at least 300 ft from the front to the back edge and around 400 feet from side to side. It moved slowly and in a straight line and took around 5 minutes to go from horizon to horizon. We were in a valley at the time, so the mountains were fairly close, and the horizons were only a few miles apart.
We are positive it was not a cloud as the sky was perfectly clear. Since there was no sound it could not have been a blimp or other man made flying object. We stood there for around 20 minutes to see if it came back or anything else would happen, but it remained quiet and uneventful. We also checked all the local new media sources for the next few days but no one else reported seeing anything that night.
We did hear of similar types of sightings in that same area at different times that year, Thank you for letting me post this and I hope it will add to all the other information you may have on similar type sightings in that area.
Witness indicates that the date of the event is approximate.  PD