Perfect disk with lights on edge; one side red, one side green: no sound No clouds, disk blocked out stars, moving S.to N.

This happened in, or around, April of 1973.  I remember that it was close to my birthday.  The weather was mild and cloudless.  I think it was a Saturday night because my parents were out.  I was almost 12, a well read and responsible kid, with no more than a passing interest in the unknown. For some reason, I went out to my front yard (the house was in the 2500 block of Southgate Blvd, Houston,TX,77025)and looked straight up.  At that moment a large disk (red lights on one side, green lights on the other, not shiny, totally silent)passed directly overhead, blotting out the stars as it passed.  It moved in a straight line over my house towards the north and I watched it until it was out of sight:  total only about 30 seconds.  As it moved away it appeared to be completely flat, and not very thick: a true disk, like a discus or a coin.  Oddly, I wasn't alarmed.  I didn't tell my parents or anyone at school.  And I pretty much forgot about it until around 1981. I know this was not the Goodyear blimp; I had seen the blimp at night in our part of the city before.  The shape was wrong, and the blimp was far from silent at that altitude. The disk was well above tree height, in that neighborhood of tall pine trees.  My closest guess on the size and altitude would be 100' across and 1000' off the ground. I am hoping that others may have seen this.