I was up on my roof stargazing on a very clear night. i'd been up there maybe 20 mins when suddenly i noticed a black triangle moving slowly across the sky, south west, in a straight line. it was travelling at a steady pace, no faster or slower than you'd expect from a commercial aircraft. i stargaze frequently in the summer, and i am familiar with planes, satellites, blimps etc. this was unlike anything i have ever seen in the sky. the craft was clearly a solid and s complete triangle, or at least very close to being complete as it blocked out the stars. it had six white lights around the edge, evenly spaced. the lights were very dim and stayed solid the whole time. there were no flashing lights, only the six solid white lights. other than this, i couldn't see any other detail on the craft. i did try and get a closer look with my binoculars but was having trouble focusing or the lenses were misted up - either way, the event only lasted approx 30 seconds so i didn't have time to figure out the problem. i can't say for sure if it was making noise or not. i live near a relatively busy road so there was car noise which made it harder to determine. also, i was so excited by what i was seeing that i was just trying to focus my binoculars to get a closer look and wasn't concentrating on sound. i'm a keen stargazer but it's hard for me to say exactly what the altitude was - if i had to guess i would say somewhere between 8-15 thousand feet. but as the event was so quick and because i couldn't make out details on the craft to give me a sense of scale, it was difficult to gage. the craft kept moving at the same pace until it went beyond my view. my initial thought was that it must be a b2 from raf fairford. the next day i contacted a friend who is one of the founders of raf fairford air day - a very popular aircraft show held at raf fairford. raf fairford is the closest military base that has a variety of aircraft, and i believe the only one that would might have aircraft that could offer a possible explanation. i explained what i saw to my friend and he couldn't tell me what it was. he said that raf fairford was at that time closed and didn't think any aircraft would be flying in or out of there. also, it seemed unusual as the lights were unlike ones i've seen on a b2 (however, i am not an aviation expert or even an aviation enthusiast so there may well be other light configurations that i am not aware of.) he couldn't give me an explanation so i trying to seek out others who might have seen it that night.