My son and I were observing stars in the clear dusk sky at about 7 pm on Sunday, Sept 20, 2015. We both noticed a long greyish object hoevering in the north sky, approx. 1/4 to 1/2 mile above the hills behind the Columbia River. It was approx. 300 to 600 feet long or maybe even larger at times because it kept changing shape. It was odd because there were no other clouds in the sky and it did not move for about 45 minutes. 2 high flying commercial jets flew near its general area, far above this object, giving us a clear point of reference to it's height. It changed shapes from a flat oblong shape to a dome shape with expansive wing looking features, then elongating horizontally, then diminshing back to a dome shape. We observed 2 or 3 smaller objects decsend from it then ascend back into it during this 45 minute period of time. This large object never moved. As the night changed from dusk to dark, the object seemed to diminsh and disappear but never moved in any direction. The lighting to take pictures was poor and my camera could not pick up the image. It was definitely artificial and not clouds or smoke rising up. My son and I both witnessed this event with a clear and rational perspective.