I saw a light shining through the clouds that looked like the inside of a reflector telescope, with a dark rounded off square with a dark line going toward one edge.

While getting ready for school, my twin sister got me to look in the sky to the south and a little west.  In the sky she should me a strange light shining through the clouds that looked like a reflector telescope, with a dark rounded off square with a dark line going toward one edge. The light was stationary as long as I was looking. I watched it as best as I could on my way to school on the buss. This happened in the summer at the begining of the school year, either in 1974 or in 1975. I think Skylab was orbiting back then.