Witnessed a cylindrical object hovering at approximately 1000 feet altitude with very little movement on a clear day. event lasted 15 mins before i lost sight of it, but not after taking video and pictures. 2 small aircraft were seen approaching the object, which seemed to be several times larger than them. it was a clear day with very little wind. no sound or lights observed. eventually it moved out of my line of sight behind some trees. it seemed to be almost dorectly over downtown amherst ma. id estimate the object to be at least 100 feet long.