was sitting on our garden bench stargazing. i noticed the object coming into view, but no flashing running lights as all other aircraft have.it was a flat round disc shape with what looked like windows all around the edge which seemed to glow from within. no other light source was visible. it moved fairly slowly until the trees blocked further viewing. viewing time probably about 15 to 20 seconds.just a rather curious object.multiple aircraft can be seen regularly.this was unique though.